HIGHWAY 
ENGINEERING 

AS   PRESENTED   AT 

The  Second   International   Road  Congress 

'  BRUSSELS,  1910 

BY 

ARTHUR  H.  BLANCHARD,  C.E.,  A.M. 

Professor  of  Highway  Engineering  in  Columbia  University  of  the  City  of  New  York\ 

Consulting  Highway  Engineer  ,•  Member  American  Society  Civil  Engineers, 

Societe  des  Enge'nieurs  Civil  de  France,  Association  Internationale 

Permanente  des  Congres  de  la  Route 

AND 

HENRY  B.   DROWNE,  C.E. 

Instructor  in  Highway  Engineering  in  Columbia  University  of  the  City  of  New  York; 
Principal  Assistant  Engineer  with  A.  H.  Blanchard;  Associate  Member 

American    Society   of  Civil  Engineers  ,•    Member  Association 
,  Internationale  Permanente  des  Congres  de  la  Route 


FIRST 

First  Thousand 


NEW  YORK:  JOHN  WILEY  &  SONS 

LONDON:    CHAPMAN  &  HALL,  LIMITED 

1911 


COPYRIGHT,  1911 

BY 
ARTHUR  H.  BLANCHARD  AND  HENRY  B.  DROWNE 


COMPOSED  AND  PRINTED  BY  THE  PUBLISHERS  PRINTING  CO.,  NEW  YORK,    U.S.A. 


DEDICATED  TO 
M.  ALBERT    MAHIEU 

Ingenieur  en  Chef  des  Fonts  et  Chaussees  de  France,  Secretaire-General 

du  Bureau  Executif  de  r Association  Internationale 

Permanente  des    Congres  de  la  Route 


241270 


PREFACE 

THE  object  of  the  authors  in  writing  this  book  was  to 
render  available  to  those  interested  in  the  progress  of  high- 
way engineering  the  large  mass  of  information  relative  to 
the  construction  and  maintenance  of  roads  and  pavements 
which  was  presented  by  the  various  reporters  and  con- 
tributors at  Brussels  in  1910. 

The  authors,  fully  appreciating  the  valuable  knowledge 
which  may  be  acquired  by  a  close  observance  of  the  practice 
of  highway  engineering  in  the  various  countries  of  the  world 
and  believing  that  it  is  possible  in  many  cases  to  profit  by 
the  successes  and  failures  of  others  who  have  worked  in 
similar  fields  and  thus  avoid  costly  duplication  of  experi- 
mental work  and  the  waste  of  public  and  private  funds 
through  the  adoption  of  methods  which  have  resulted  in 
unsatisfactory  roads  and  pavements,  wish  to  emphasize  the 
fact  that  the  subject  of  foreign  practice  has  not  received  the 
attention  it  deserves  by  American  engineers. 

The  main  part  of  the  book  is  devoted  to  the  presenta- 
tion of  the  fundamental  facts  and  salient  opinions  contained 
in  the  one  hundred  and  twenty-four  papers,  aggregating 
over  two  thousand  pages,  submitted  to  the  Congress  and  the 
discussions  at  the  many  sessions  of  the  Congress  which 
occupied  over  two  hundred  pages  of  the  "  Report  of  the 
Proceedings  of  the  Congress,"  recently  published  by  the 


VI  PREFACE 

Association.  It  should  be  borne  in  mind  that  the  reporters 
selected  by  the  Executive  Committee  were  instructed  to 
cover  in  their  reports  the  progress  in  the  particular  field 
assigned  relative  to  the  practice  of  the  countries  which  they 
represented.  The  conclusions  which  were  finally  adopted 
by  the  Congress  were  the  outcome  of  thorough  consideration 
and  ofttimes  strenuous  debates  by  highway  engineering 
experts  from  all  parts  of  the  world.  It  is  self-evident  that 
through  the  medium  of  an  International  Road  Congress  a 
very  comprehensive  review  of  foreign  practice  is  presented. 

The  plan  adopted  in  the  compilation  of  the  book  has 
been  to  collate  the  material  under  headings  familiar  to 
American  engineers.  Discussions  in  every  case  follow  the 
reporter's  name,  hence  quotation  marks  were  not  used 
although  in  some  cases  the  words  of  the  reporters  were 
employed,  but  generally  the  object  of  the  authors  was  at- 
tained by  presenting  the  important  ideas  of  the  reporters 
in  abstract.  The  discussions  on  a  given  topic  relative  to 
the  practice  in  a  given  country  have  been  congregated  while 
the  groups  thus  formed  have  been  arranged  in  alphabetical 
order  in  each  chapter. 

As  some  readers  may  desire  to  communicate  with  the 
reporters,  the  names,  titles  and  addresses  of  all  contributors 
to  the  discussions  on  a  given  topic  have  been  listed  at  the 
beginning  of  each  chapter  as  well  as  being  given  in  connec- 
tion with  the  list  of  reports  and  communications  on  the 
various  questions  in  Chapter  I. 

The  United  States  standard  equivalents  of  the  various 
foreign  monetary  values,  weights  and  measures  have  been 


PREFACE  vii 

given  in  order  to  facilitate  the  comparison  of  the  practice 
and  cost  data  presented  by  engineers  from  many  countries. 
The  authors  are  under  obligations  to  Messrs.  Earl  R. 
Donle,  Clifford  M.  Hathaway,  and  Irving  W.  Patterson  for 
valuable  assistance  rendered  in  connection  with  the  collab- 
oration of  the  book,  translations  and  proof-reading. 

Columbia  University, 

NEW  YORK  CITY,  A.  H.  B. 

August  15,  1911.  H.  B.  D. 


CONTENTS 

PAGE 

PREFACE »    .    .     .        v 

Part  I 

INTRODUCTORY 

CHAPTER 

I.  The  Congress      .    ..." 1 

II.  The  Exhibition   .     .     . 29 

III.  The  Excursions  and  Receptions 34 

Part  II 

TECHNICAL    DISCUSSIONS 

IV.  Economics  of  Highway  Engineering   ....     38 
V.  Traffic  Census 53 

VI.  Materials  of  Highway  Engineering     ....  59 

VII.  Foundation  and  Drainage 76 

VIII.  Macadam  and  Gravel  Roads 88 

IX.  Dust  Prevention  by  the  Use  of  Palliatives  .     .  93 

X.  Bituminous  Surfaces 97 

XI.  Bituminous  Pavements 109 

XII.  Brick,  Concrete,  Stone  Block  and  Wood  Block 

Pavements 130 

ix 


X  CONTENTS 

CHAPTER  PAGE 

XIII.  Trackways 141 

XIV.  Footways  in  Towns  and  Cities       .     .     .     .     .144 
XV.  Road  Machinery  and  Tools       .     .     ...     .     .150 

XVI.  Garbage  Removal,  Cleaning  and  Watering      .  161 
XVII.  Removal  of  Snow  and  Ice     .     .     .    ...     .  171 

XVIII.  Road  Signs 183 

XIX.  Pipe  Systems  in  Roads  and  Streets    .     .     .     .189 

XX.  Tramways  on  Roads  and  Streets 197 

XXI.  Public  Service  Conveyances 210 

XXII.  Highway  Bridges     .     .     .  •  .    .     .     ...     .  219 

XXIII.  Tires 225 

XXIV.  Conclusions  Adopted  at  the  Second  Congress  .  232 

APPENDIXES 

I.  Proceedings  of  the  Permanent  International 

Commission     .     .     .     .     .     .     .     .     .     .  \  244 

II.  Regulations  of  the  Permanent  International 

Association  of  Road  Congresses    ....  247 


HIGHWAY  ENGINEERING 


Part  I 
INTRODUCTORY 


CHAPTER  I 

THE    CONGRESS 

The  First  International  Road  Congress  was  held  at 
Paris  in  1908  under  the  auspices  of  the  French  Govern- 
ment. It  was  attended  by  over  2,250  persons  affiliated 
with  various  branches  of  highway  engineering.  The  world- 
wide interest  in  the  proceedings  of  the  Congress  was 
shown  by  the  participation  of  representatives  from  twenty- 
seven  countries  in  the  discussion  at  the  various  sessions. 
A  total  of  ninety-eight  papers  covering  many  phases  of 
highway  engineering  and  allied  subjects  were  prepared 
for  this  Congress. 

At  the  plenary  sitting  of  the  First  Congress  held  on 
October  17th,  1908,  the  following  resolutions  were  adopted 
creating  the  Permanent  International  Association  of  Road 
Congresses. 

1.  A  Permanent  International  Commission  of  Con- 
gresses is  established  with  the  object  of  furthering  progress 
in  the  construction,  maintenance,  and  use  of  the  road, 

i 


*** 

ENGINEERING 


and  also  of  providing  in  the  future  for  continuity  in  the 
work  of  the  Congress. 

2.  This  Commission  is  composed  of  members  includ- 
ing:— (a)  The    governments,    societies,  and    other    public 
bodies  of  all  countries.     (6)  Individual  members. 

3.  The  Governing  Body  of  this  Commission  is  pro- 
visionally  a   Permanent   International   Council   composed 
of    the    Presidents    and    Vice-Presidents    of    the    General 
Board  and  of  the  Sectional  Boards  of  the  First  International 
Road  Congress  held  at  Paris  in  1908. 

4.  This  Permanent  Council  is  in  its  turn  administered 
by  a  provisional  Standing  Board  which  shall  sit  at  Paris. 

Each  country  is  represented  on  this  Board  by  one 
or  two  members  of  the  Permanent  Council.  The  pro- 
ceedings of  the  Board  will  be  prepared  and  carried  out 
by  an  Executive  Committee,  sitting  at  Paris  and  composed 
of  three  members:— 

M.  LETHIER,  Inspector-General  of  Bridges  and  Roads 
of  France,  President. 

M.  BALLIF,  President  of  the  Touring  Club  of  France, 
Vice-President. 

M.  MAHIEU,  Chief -Engineer  of  Bridges  and  Roads  of 
France,  Secretary. 

5.  The  Permanent  Council  is  charged  with  the  draw- 
ing up   of  the   Statutes  of  the  Permanent   International 
Commission  of  Road  Congresses  and  with  the  immediate 
application  of  these  statutes. 

6.  The  Permanent   Council  is   charged  with   the   or- 
ganization of  the  next  Road  Congress,  which  will  be  held 
at  Brussels  in  1910. 

7.  The    Permanent    Council    is    instructed    to    study 
the  question  whether  it  would  not  be  desirable  to  centralize 


THE    CONGRESS  3 

in  a  special  organization  the  results  obtained  from  the 
various  experiments  made  in  all  countries,  and,  if  necessary, 
to  cause  new  experiments  to  be  undertaken,  and,  further, 
to  institute  chemical  and  mechanical  experiments  in  tar 
and  other  materials  (as  is  done  for  materials  of  construc- 
tion, such  as  steel,  cement,  etc.),  with  a  view  to  fixing  a 
standard  for  such  substances. 

The  Second  International  Road  Congress  was  held 
in  Brussels  from  July  31st  to  August  7th,  1910,  under 
the  patronage  of  His  Majesty  the  King  of  the  Belgians, 
ALBERT  I. 

The  Congress  was  presided  over  by  the  President, 
M.  Lagasse  de  Locht,  Director-General  of  Bridges  and  Roads 
of  Belgium,  while  M.  E.  Walin,  Chief  Engineer  of  Bridges 
and  Roads  and  Director  of  Highways  to  the  Ministry  of  Public 
Works  of  Belgium,  officiated  as  General  Secretary. 

The  total  number  of  members  of  the  Second  Congress 
was  2,118  representing  thirty-eight  countries.  The  table 
of  membership  at  the  end  of  this  chapter  contains  interest- 
ing information  relative  to  the  distribution  of  members 
among  the  various  countries  and  the  classification  of 
members. 

The  following  program  gives  the  questions  discussed 
and  a  list  of  the  authors  and  the  titles  of  the  124  reports 
and  communications  presented  at  the  Second  Congress. 


4  HIGHWAY     ENGINEERING 

SECTION  I 

CONSTRUCTION  AND   MAINTENANCE 

SUB-DIVISION  A:    CONSTRUCTION  AND  MAINTENANCE 
OUTSIDE  THE  LARGE  TOWNS 

First,  Second  and  Third  Questions 

Third  Communication 
Norway 

1.  SKOUGAARD,  J.,  Director  General  of  Bridges  and 
Roads,  Christiania.  Metalled  and  paved  roads  in 
Norway;  materials  used  in  their  construction  and 
maintenance. 

First  Question 

METALLED  AND  PAVED  ROADS.  USE  OF  BINDING 
MATERIALS  IN  THE  CONSTRUCTION  OF  METALLED  ROADS. 
USE  OF  TRACKWAYS  IN  THE  PAVED  ROADS.  PROGRESS 
MADE  IN  COMBATING  WEAR  AND  TEAR  AND  DUST 

1.  General  Reporter,  M.  MACQUET,  Chief  Engineer  and 
Director  of  Bridges  and  Roads,  Brussels. 

Germany 

2.  SPERBER,  Chief  Engineer,  Hamburg,  and 
FRANZE,  GUSTAV,  Commissioner  of  Public  Works, 
Frankfort-on-the-Main.     Diminution  of  the  dust- 
plague  on  the  public  roads  of  German  cities. 

Austria 

3.  BRADACZEK,  THEODOR,   Imperial   Commissioner   of 
Public  Works,  Prague.    Construction  and  mainte- 
nance of  the  Imperial  Roads  in  the  Kingdom  of 
Bohemia. 


THE    CONGRESS  5 

Belgium 

4.  FROIDURE,  EUGENE,  Principal  Engineer  of  Bridges, 
and  Roads,  Ypres,  and 

VERSTRAETE,  RICHARD,  Engineer  of  Bridges  and 
Roads,  Bruges.  Structure  of  metalled  roads  in 
Belgium;  various  methods  of  tar  painting  roads  in 
Belgium;  watering  with  chloride  of  calcium  and 
resurfacing  with  use  of  tar. 

Bulgaria 

5.  KARAKOULAKOFF,    PAUL,    Engineer,    Ministry     of 
Public   Works,   Sofia.     The    country   highroads  in 
the  Kingdom  of  Bulgaria. 

Spain 

6.  SANCHIS,  VINCENT,  Engineer  of  Highways,   Canals 
and  Harbors,  Valencia.     Metal  trackways  for  or- 
dinary vehicles. 

United  States 

7.  BLANCHARD,  ARTHUR  H.,  M.  Am.  Soc.  C.  E.,  Deputy 
Engineer,    Rhode    Island    State    Board    of    Public 
Roads,   Providence,   R.   I.     Investigations   of    the 
use  of  various  bituminous  binders  in  the  construc- 
tion of  State  Roads  in  Rhode  Island. 

United  States 

8.  CROSBY,  WALTER  W.,  M.  Am.  Soc.  C.  E.,  Chief  Engi- 
neer to  the  Maryland  Geological  and  Economic  Survey, 
Baltimore,  Md.     The  use  of  binding  materials  in 
the  construction  of  macadamized  roadways. 

United  States 

9.  FLETCHER,  AUSTIN  B.,  M.  Am.  Soc.  C.JE.,  Secretary, 
Massachusetts  Highway  Commission,  Boston,  Mass. 
Protective  coatings  for  macadam  roads. 


6  HIGHWAY   ENGINEERING 

United  States 

10.  HOOKER,  S.  PERCY,   Chairman,  New    York   High- 
way   Commission,    Albany,    N.    Y.     Maintenance 
and  repair  of  stone  roads  in  the  United  States. 

United  States 

10  bis.  PARKER,  HAROLD,  M.  Am.  Soc.  C.  E.,  Chairman, 
Massachusetts  Highway  Commission,  Boston,  Mass. 
Description  of  the  method  of  building  a  road  to 
meet  the  requirements  of  modern  traffic  in  the 
United  States. 

France 

11.  LEGAVRIAN,    P.,   Engineer  of  Bridges  and  Roads, 
Versailles.      Metalled   and   paved   roads.     Use   of 
binding  materials  in  the  construction  of  metalled 
roads.     Use    of    trackways    in    the    paved    roads. 
Progress  made  in  combating  wear  and  tear  and 
dust. 

France 

12.  SAUNIER,  HONORS,  District  Inspector,  Rouen.  Hy- 
draulic binders  for  macadam  roads.     Trackways. 
Progress  in  combating  wear  and  tear  and  dust. 

Great  Britain 

13.  DRUMMOND,  ROBERT,    County   Surveyor,  Renfrew- 
shire,   Paisley,     Scotland.     Metalled    and    paved 
roads   in   Scotland.     Use   of   trackways   in   paved 
roads. 

Hungary 

14.  GLASNER,  ANTOINE,  Engineer,  Budapest.     Metalled 
roads  and  paved  roads  outside  the  large  towns  in 
Hungary. 


THE    CONGRESS  7 

Italy 

15.  TEDESCHI,  MASSIMO,  Engineer,  Turin,  and  CORAZZA, 
CESARE,  Engineer,  Turin.  Metalled  roads  in 
Italy. 

Switzerland 

16.  ETIER,  PAUL,  Councilor  of  State,  Lausanne.     Met- 
alled roads  in  Switzerland.     Progress  of  the  fight 
against  wear  and  tear  and  dust. 

Second  Question 

FOUNDATION  AND  DRAINAGE  OF  ROADS.     METHODS  OF 
CARRYING  OUT  THE  WORK 

II.  General   Reporter:     MICHEZ,    H.,    Chief  Engineer 
and  Director  of  Bridges  and  Roads,  Arlon.  j 

Austria 

17.  BOLTZ,   JOHANN,   Imperial    Chief   Commissioner  of 
Public  Works,   Laibach.     Construction  and  main- 
tenance of  the  Imperial   Roads  in  the   Duchy  of 
Carniola. 

Belgium 

18.  VAN   VOLSOM,   EDGARD,  Engineer  of  Bridges  and 
Roads,  Brussels.     Foundation  of  roads.     Methods 
of  carrying  out  the  work  in  Belgium. 

United  States 

18  bis.  PIERCE,  VERNON  M.,  Chief  Engineer  U.  S. 
Office  of  Public  Roads,  Washington,  D.  C.  The 
foundation  and  drainage  of  country  roads  in  the 
United  States. 


8  HIGHWAY   ENGINEERING 

France 

19.  PIERRET,  LEOPOLD,  Chief  Engineer  of  Bridges  and 
Roads,  Amiens.     Systems  of  foundation  and  drain- 
age of  metalled  and  paved  roads. 

France 

20.  LELIEVRE,  CHARLES,  Honorary  District   Inspector, 
Versailles.     Foundations    and    drainage    of   roads. 
Investigations  on  the  foundation  systems  in  France. 

Italy 

21.  VANDONE,  ITALO,   Chief  Engineer  of  the  Province 
of  Milan.     Foundation  and  drainage  of  the  road 
from  Binasco  to  Rosate,  Province  of  Milan. 

Third  Question 

LAYING  LIGHT  RAILWAYS  AND  TRAMWAYS  ON  ROADS. 
ADVANTAGES  AND  DISADVANTAGES.  EFFECT  ON  THE  VARI- 
OUS METHODS  AND  THE  COST  OF  MAINTENANCE 

III.  General  Reporter:  BONNEVIE,  AUGUSTS,  Chief 
Engineer  of  Railroads,  Brussels. 

Germany 

22.  GERLACH,    FRIEDRICH,    Imperial    and    Municipal 
Commissioner    of   Public    Works,    Berlin.     Laying 
light  railways  and  tramways  on  roads  with  special 
consideration  of  municipal  roads. 

Austria 

23.  ULLMAN,  G.,  Chief  Engineer  of  Tramways,  Vienna. 
Laying  light  railways  and  tramways  on  Austrian 
roads. 


THE    CONGRESS  9 

Spain 

24.  SPITERI,  JOSE  RODRIGUEZ,  Chief  Engineer  of  High- 
ways, Canals  and  Harbors,  Malaga.     Laying  light 
railways  and  tramways  on  Spanish  roads. 

France 

25.  GALLIOT,  FRANgois,  Chief  Engineer  of  Bridges  and 
Roads,  Dijon.     Laying  light  railways  and  tramways 
on  roads.     Advantages  and  disadvantages.    Effect 
on  the  system  and  on  the  cost  of  maintenance. 

Great  Britain 

26.  WYNNE-ROBERTS,  R.  O.,  M.  Inst.  C.  E.,  F.  R. 
San.  Inst.,  Westminster,  London,  England.     Lay- 
ing light  railways  in  Great  Britain. 

Hungary 

27.  VON  SZTROKAY,  STEFAN,  Chief  Engineer,  Budapest. 
Laying  light  railways  and  tramways  on  roads  in 
Hungary.     Advantages  and  disadvantages.    Effect 
on  the  system  and  on  the  cost  of  maintenance. 

Italy 

28.  TOLLER,    GINO,   Engineer,  Milan.     Light  railways 
and  tramways  on  the  roads  in  Italy. 

Netherlands 

29.  GELINCK,  W.  G.  C.,  Engineer  of  Waterways,  Assen, 
and 

VAN  HEYST,  D.  A.,  Engineer  of  Waterways,  Ziitphen. 
The  tramways  and  National  Roads  of  the  Nether- 
lands. 


10  HIGHWAY   ENGINEERING 

SUB-DIVISION   B:  CONSTRUCTION  AND  MAINTENANCE 
IN  THE  LARGE  TOWNS 

Fourth  Question 

CLEANSING  AND  WATERING.  NECESSITY  OR  UTILITY. 
METHODS  IN  USE.  THEIR  COST.  COMPARISON  OF  VARIOUS 
METHODS 

IV.  General  Reporter:  LOPPENS,  GEORGES,  Engineer, 
Provincial  Engineering  Department,  Liege. 

Germany 

30.  HOPFNER,    PAUL,   Imperial   and    Municipal   Com- 
missioner of  Public  Works,  Cassel.     Cleansing  and 
watering.     Necessity  or  utility.     Methods  in  use. 
Their  cost.     Comparison  of  various  methods. 

Austria 

31.  KELLNER,   DR.    HANS,   Director   of  Public   Works, 
Brlinn.     Cleansing  and  watering  oa  Austrian  roads. 

Spain 

32.  SPITERI,  JOSE  RODRIGUEZ,  Chief  Engineer  of  High- 
ways, Canals  and  Harbors,  Malaga.     Cleansing  and 
watering  on  Spanish  roads. 

France 

33.  BRET,   E.,   Chief  Engineer  of   Bridges  and  Roads, 
Paris.     Road  scavenging,   cleansing  and  watering 
in  large  cities  of  France. 

Great  Britain 

34.  YABBICOM,    THOMAS    H.,    M.    Inst.    C.    E.,    City 
Engineer,  Bristol,  England.     Cleansing  and  water- 
ing streets  in  the  great  towns  of  England,  Scotland 
and  Ireland. 


THE    CONGRESS  11 

Hungary 

35.  BALLO,  ALFRED,  Commissioner   of  Street  Cleaning, 
Budapest.     Street  cleaning    methods  in  the    City 
of  Budapest. 

Monaco 

36.  BERTHET,  E.,  Councilor  of  State,  Monaco.     Cleans- 
ing and  watering;    necessity  or  utility;    methods 
in  use;    their  cost;    investigations  on  the  roads  of 
the  Principality  of  Monaco. 

Norway 

37.  ROSHAUW,  J.  C.,  Director  of  Highways,  Christiania. 
Road     scavenging,    cleansing     and     watering     in 
Christiania. 

Fifth  Question 

CHOICE  OF  THE  SURFACING  MATERIALS. 

V.  General  Reporter,  LEMEUNIER,  R.,  Chief  Engineer 
and  Director  of  Highways,  Antwerp. 

Germany 

38.  BREDTSCHNEIDER,    AUGUST,    Commissioner,   Board 
of  Public  Works,  Charlottenburg; 
HORBURGER,    Member,    Board    of   Public    Works, 
Munich; 

EISENLOHR,  Director,  Board  of  Public  Works, 
Strasburg; 

FLECK,  GEORG,  Commissioner,  Board  of  Public 
Works,  Dresden.  Inquiry  on  the  methods  of 
surfacing  highways  in  the  German  towns  exceed- 
ing 50,000  inhabitants. 


12  HIGHWAY  ENGINEERING 

Belgium 

39.  DE  JAEGERE,  ALBERIC,  Civil  Engineer,  Antwerp. 
Different  methods    of    road  surfacing  as  used  in 
the  large  cities  of  Belgium. 

Egypt 

40.  LLOYD  DAVIES,  D.  E.,  M.  Inst.  C.  E.,  Chief  En- 
gineer  to   the   Municipality   of  Alexandria.     Road 
making  in  Alexandria. 

Spain 

41.  LAFARGA,  PROSPERO,  Engineer  of  Highways,  Canals 
and  Harbors,   Alicante.     Choice   of   the   surfacing 
materials;    experiments  made  and  results  obtained 
in  some  Spanish  towns. 

United  States 

42.  RABLIN,  JOHN  R.,  M.  Am.  Soc.  C.  E.,  Chief  En- 
gineer,     Metropolitan     Park    Commission,    Boston, 
Mass.     Construction  and  maintenance  of  parkway 
roads  in  the  United  States. 

France 

43.  MAZEROLLE,  L.,  Engineer  of  Bridges   and  Roads, 
Paris.     Research   of   the   form   of   surface   to    be 
employed  for  a  large  city;  factors  to  be  taken  into 
account  when  making  a  choice.    Various  methods 
of  surfacing  roads;    advantages  and  disadvantages 
of  the  surfaces  used  in  Paris.     Surfacing  footways. 

Great  Britain 

44.  CROMPTON,  COL.  R.  E.,  M.  Inst.    C.    E.,    Royal 
Automobile  Club,  London,  England.     On  the  con- 
struction   and   maintenance    of   the   roadways    of 
large  towns  in  England. 


THE    CONGRESS  13 

Great  Britain 

45.  GULLAN,  HECTOR  F.,  Superintendent  of  the  Works 
Department   of   the    City   and   County   Borough   of 
Belfast,  Ireland.     Choice  of  the  surface  and  of  the 
system  of  construction;    first  capital  expenditure, 
vitality  and  maintenance  cost  of  various  surfaces 
employed  in  Great  Britain. 

Hungary 

46.  FOCK,  EDOUARD,  Chief  Engineer,  Budapest. 

MENCZER,  BELA,  Chief  Engineer,  Budapest.  Con- 
struction and  maintenance  of  the  roads  -of  large 
towns  in  Hungary.  Choice  of  the  surfacing  ma- 
terials. 

Italy 

47.  CATTANEO,  PAOLO,  Engineer,    Office  of  Municipal 
Engineer,  Milan.     Stone  pavements  in  Italy. 

Switzerland 

48.  WENNER,  VICTOR,  City  Engineer,  Zurich. 

SCHLAEPFER,  ARTHUR,  Street  Inspector,  Zurich. 
Choice  of  the  road  surfacing  materials  in  Switzer- 
land. 

Sixth  Question 

METHODS  OF  CARRYING  OUT  ROAD  WORK  IN  CONNEC- 
TION WITH  LIGHTING  AND  WATER  SUPPLY 

VI.  General    Reporter,    FOURMANOIS,    A.,    Engineer, 
Technical  Department  of  the  Province  of  Brabant,  Brussels. 


14  HIGHWAY   ENGINEERING 

Germany 

49.  PETERS,    FRITZ,    Commissioner    of   Public    Works, 
Magdeburg; 

STEUERNAGEL,     KARL,     Commissioner     of    Public 

Works,  Cologne; 

VON  SCHOLTZ,  A.,  Commissioner  of  Public  Works, 

Breslau; 

VON   MONTIGNY,   Commissioner   of  Public  Works, 

Aix-la-Chapelle;  and 

HENTRICH,  HUBERT,  Commissioner  of  Public  Works, 

Crefeld.     Method   of   carrying  out  road   work  in 

connection  with  lighting  and  water  supply. 

Belgium 

50.  LEMEUNIER,  RICHARD,   Chief  Engineer   of  Bridges 
and  Roads,  Antwerp. 

DE  HEEM,  PAUL,  Engineer  of  Bridges  and  Roads, 
Antwerp.  Method  of  carrying  out  road  work  in 
connection  with  lighting  and  water  supply  at 
Antwerp. 

France 

51.  LIDY,    GEORGES,    Chief  Engineer    of  Bridges    and 
Roads,    Bordeaux.      City    streets;     how    they    are 
controlled  and  administered;    method  of  carrying 
out  the  works;  their  effect  on  the  suitability  of  the 
street  to  the  traffic. 

Great  Britain 

52.  SILCOCK,    EDWARD    JOHN,    Past    President    of   the 
Society  of  Engineers,  Westminster,  London,  England. 
Methods  of   carrying  out  road  maintenance   and 
repair  work  in  connection  with  underground  pipes. 


THE    CONGRESS  15 

Hungary 

53.  MIHALYFI,  JOSEPH,  Technical  Councilor,  Budapest, 
and 

JASZ,  DIDIER,  Technical  Councilor,  Budapest. 
Lighting  and  water  supply  in  connection  with 
road  construction  in  Budapest. 

Netherlands 

54.  WALL  AND,   C.   B.    J.,   Engineer   of  Public    Works, 
The    Hague.     Method    of    construction    of    roads 
along  tram  lines  within  city  areas. 


SECTION   II 

USE   AND   TRAFFIC 

Seventh  Question 

INFLUENCE  OF  WEIGHT  AND  SPEED  OF  VEHICLES  ON 
BRIDGES  AND  OTHER  SPECIAL  STRUCTURES 

VII.  General   Reporter,  CHRISTOPHE,  PAUL,  Principal 
Engineer  of  Bridges  and  Roads,  Brussels. 

Belgium 

55.  DESCANS,   LEON,  Engineer   of  Bridges  and  Roads, 
Ghent.     The  influence  of  the  weight  and  speed  of 
vehicles  on  the  strength  of  bridges. 

France 

56.  RESAL,    JEAN,    Inspector-General    of    Bridges    and 
Roads,   Paris.     Influence   of  weight  and  speed   of 
vehicles   on   the   stability   and   upkeep   of   special 
structures. 


16  HIGHWAY   ENGINEERING 

Great  Britain 

57.  BEAUMONT,  W.  WORBY,  M.  Inst.  C.  E.,  Consulting 
Engineer,    London,   England.     Influence   of   speed 
and  weight  of  vehicles  on  bridges  and  other  struct- 
ures. 

Hungary 

58.  DE  NOVAK,  FRANgois,  Technical  Councilor  to  the 
Royal   Ministry,    Budapest.     Influence    of   weight 
and  speed  of  vehicles  on  special  structures. 

Eighth  Question 

ROAD  VEHICLES:  CONDITIONS  TO  BE  FULFILLED  BY 
HORSE  OR  MECHANICALLY  DRIVEN  VEHICLES  IN  ORDER 
THAT  THEY  MAY  NEITHER  CAUSE  NOR  SUFFER  ANY  EXTRA- 
ORDINARY DAMAGE  TO  OR  FROM  THE  ROAD 

VIII.  General  Reporter,  HEIRMANN,  EDMOND,  En- 
gineer, Brussels. 

France 

59.  LUMET,   GEORGES,    Engineer  of  Arts   and   Manu- 
factures,  Paris.     Road  vehicles. 

Great  Britain 

60.  MALLOCK,  A.,  E.  R.  S.,  Royal  Automobile    Club, 
London,    England.     Relative    effect    on    roads    of 
hard  and  soft  tires. 

Netherlands 

61.  STEFFELAAR,  L.  C.,  President  of  the  Touring   Club 
of  Netherlands. 

JANSON,  J.  H.,  Secretary  of  the  Touring   Club   of 
Netherlands.    Some    experiments  to    ascertain  the 


THE    CONGRESS  17 

influence  of  the  width  of  the  tires  of  wheels  of 
vehicles  upon  the  more  or  less  rapid  destruction 
of  road  coverings  and  upon  the  tractive  force  of 
vehicles. 

Ninth  Question 

CONDITIONS  FOR  THE  USE  OF  PUBLIC  SERVICE  CON- 
VEYANCES OTHER  THAN  TRAMWAYS!  ADVANTAGES  AND  DIS- 
ADVANTAGES, CAPACITY,  COST,  ETC. 

IX.  General  Reporter,  HANSEZ,  JULES,  President, 
Touring  Committee,  Royal  Automobile  Club,  Brussels. 

Belgium 

62.  DE  FUISSEAUX,  H.  L.,  Chief  Engineer  and  Director, 
Autobus   Company,   Brussels.     Conditions   for   the 
exploitation    of   public    service   road   conveyances 
other  than  tramways. 

France 

63.  MARIAGE,  A.,  Chief  Engineer,  Omnibus    Company, 
Paris.     Conditions  for  the  use   of  public   service 
conveyances    other    than    tramways.     Advantages 
and  disadvantages.     Capacity,  cost,  etc.     Investi- 
gations on  the  conditions  in  France. 

France 

64.  PERISSE,    LUCIEN,    Engineer  of  Arts   and   Manu- 
factures, Paris.     Operation  of  automobiles  as  public 
service  conveyances. 

Great  Britain 

65.  SMITH,  EDWARD  SHRAPNELL,  Member  of  Committee, 
Royal  Automobile  Club,  London,  England.     Motor 
omnibus  or  electric  tramcar? 


18  HIGHWAY   ENGINEERING 

Hungary 

66.  DE  HEVESY,  GUILLAUME,  Civil  Engineer,  Budapest. 
Economical  transport  of  industrial  goods. 

Italy 

67.  ALBERTINI,  ANTOINE,  Director  of  Engineering   De- 
partment,   Province     of    Modena.     Conditions    for 
the  use  of  public  service  conveyances  other  than 
tramways  in  Italy. 


COMMUNICATIONS 

SPECIAL  REPORTS 


United  States 


1.  PENNYB ACKER,  JAMES  E.  JR.,  Chief  of  Road  Manage- 
ment, Office  of  Public  Roads,  U.  S.  Department  of 
Agriculture,  Washington,  D.  C.  Road  administra- 
tion in  the  United  States. 

Great  Britain 

1. bis.  WAKELAM,  H.  T.,  M.  Inst.  C.  E.,  County  Engineer 
of  Middlesex,  Westminster,  London,  England.  The 
rule  of  the  road. 


THE    CONGRESS  19 

SECTION  I 

CONSTRUCTION  AND   MAINTENANCE 
First  Communication 

USE  OF  MECHANICALLY  DRIVEN  PETROL  MOTOR  ROLLERS 

Belgium 

2.  THOMAS,  EDMOND,  Civil  Engineer,  Brussels.    Petrol 
motor  road  rollers. 

France 

3.  PELLE,   C.   F.  J.,  Engineer  of  Bridges  and   Roads, 
Paris.     The    employment   of   oil   or    petrol    driven 
road  rollers. 

Great  Britain 

4.  WAKELAM,  H.  T.,  M.  Inst.  C.  E.,  County  Engineer 
of    Middlesex,     Westminster,      London,      England. 
Petrol  motor  rollers. 

{ 
Second  Communication 

ROAD  MAKING  TOOLS  AND  IMPLEMENTS  OTHER  THAN 
MECHANICALLY  DRIVEN  ROLLERS,  SCARIFIERS,  ETC. 

Austria 

5.  MACHNITSCH,    RUDOLF,    Imperial    Chief   Engineer, 
Gorz.     Road    making    tools    and    implements    in 
Austria. 

France 

6.  PONS,  ALFRED,  District  Inspector,  Montpellier.    Road 
making  tools  and  implements  other  than  road  rollers. 


20  HIGHWAY  ENGINEERING 

France 

7.  VERGER,  CASIMIR,  Assistant  Engineer  of  Bridges  and 
Roads,  Paris.     Road  plant  of  the  City  of  Paris. 

Italy 

8.  GOLA,   EMILIO,  Engineer,    Milan.     Road    cleaning 
machines. 

Russia 

9.  WAICHT,  CESLAV,  Engineer  of  Highways,  Warsaw. 
Machines  employed  in  Russia  for   the  repair  and 
maintenance  of  roads. 

Third  Communication 

VARIOUS  MATERIALS  IN  USE  FOR  THE  PURPOSE  OF 
CONSTRUCTION  AND  MAINTENANCE.  CONDITIONS  TO  BE 
FULFILLED.  TESTS,  UNITS  TO  BE  ADOPTED 

Germany 

10.  BREDTSCHNEIDER,  AUGUST,  Commissioner  of  Public 
Works,    Charlottenburg.     Laboratory    tests    made 
with  various  asphaltic  materials. 

Austria 

11.  WALBAUM,    LUDWIG,    Imperial     Commissioner    of 
Public  Works,  Gratz.     Special  study  of  the  roads 
of  Styria. 

Belgium 

12.  CORNU,  Louis,  Principal   Engineer  of  Bridges  and 
Roads,  Arlon,  and 

CAMERMAN,  EMILE,  Engineer,  Brussels.  Various 
materials  in  use  for  the  purpose  of  construction 
and  maintenance;  conditions  to  be  fulfilled;  tests. 


THE   CONGRESS  21 

Spain 

13.  BORES  Y  ROMERO,    DON  JOSE,  Chief  Engineer   of 
Highways,   Canals  and  Harbors,   Lerida.     Various 
materials  in  use  for  the  purposes  of  construction 
and  maintenance;   conditions  to  be  fulfilled;   tests. 

United  States 

14.  HUBBARD,  PREVOST,  Chemist,  Office  of  Public  Roads, 
Washington,    D.    C.     The   physical   and   chemical 
characteristics  of  bituminous  road  materials. 

United  States 

15.  Ross,  CHARLES  W.,  Street  Commissioner,  Newton, 
Mass.     Difficulties  of  road  building  in  the  United 
States. 

France 

16.  MESNAGER,    AUGUSTIN,  Chief  Engineer  of  Bridges 
and   Roads,    Paris.     Natural    stones   used   in   the 
construction  and  maintenance  of  roads. 

Great  Britain 

17.  WYNNE-ROBERTS,    R.  0.,  M.   Inst.  C.  E.,  F.  R. 
San.  Inst.,  Westminster,  London,  England.    Various 
materials  in  use  for  the  purposes  of  construction 
and    maintenance    of    roads.     Conditions    to    be 
fulfilled.    Units  to  be  adopted. 

Italy 

18.  TOURING     CLUB    OF    ITALY.    Actual    studies    in 
Italy  on  the  coefficients  of  quality  .of  metalling 
materials. 


22  HIGHWAY   ENGINEERING 

Netherlands 

19.  VAN  LOBEN  SELS,  M.  J.,  Vice-President,  Netherlands 
Association    of    Brick    Manufacturers,    Nimwegen. 
Method   followed   in   Holland   to   make   roads   of 
greater  resisting  power. 

Russia 

20.  TSVETKOVSKY,  CONSTANTIN,  Engineer  of  Highways, 
Warsaw.     The  use  of   vitrified  clinker   bricks  for 
the  purpose  of  construction  and  maintenance  of 
roads  in  Russia. 

Russia 

21.  MIKHAILOFF,    PAUL,    Engineer    of  Highways,    St. 
Petersburg.     Remarks  on  Russian  roads. 

Fourth  Communication 

CONSTRUCTION  OF  FOOTWAYS  IN  TOWNS 

France 

22.  LE    Roux,     NICOLAS,    Engineer    of    Bridges    and 
Roads,  Angers.     The  laying  down  of  footpaths  in 
towns. 

Great  Britain 

23.  TRUSLER,  GEORGE  D.,  A.  M.  C.  E.,  Civil  Engineer, 
London,    England.     Footpaths    in    the    City    of 
London. 

Netherlands 

24.  HENDRICKS,  C.  J.,  Manufacturer  of  Paving  Bricks, 
Woerden.     Sidewalks  paved  with  brick. 


THE    CONGRESS  23 

Portugal 

25.  ROLDAN  Y  PEGO,  MANUEL,  Engineer,  Lisbon,  and 
MELLO     DE    MATTOS,    JOSE,    Engineer,    Lisbon. 
Footways  of  small  setts.     The  paving  of  public 
places  and  sidewalks  in  Lisbon. 

Fifth  Communication 

REMOVAL  OF  SNOW  AND  ICE 
Austria 

25  bis.    SPANGLER,  LUDWIG,    Municipal    Director    of 
Streets,  Vienna.     Removal  of  snow. 

Belgium 

26.  COURTOIS,  AUGUSTS,  Principal  Inspector  of  Bridges 
and  Roads,  Bastogne.     Removal  of  snow  and  ice. 

France 

27.  MAZEROLLE,  L.,  Engineer  of   Bridges  and   Roads, 
Paris.     Investigations  on  the  removal  of  snow  in 
Paris. 

France 

28.  WILHELM,   IVAN,    Chief  Engineer    of    Bridges  and 
Roads,  Gap.     The  removal  of  snow  and  ice  outside 
of  towns 

Italy 

29.  CINQUE,  VICTOR,    Chief  Engineer    of  the  Province 
of  Brescia.     Removal  of  snow  and  ice  in  Italy. 

Russia 

30.  MIKHAILOFF,    PAUL,    Engineer    of    Highways,    St. 
Petersburg.     Removal  of  snow  in  Russia. 


24  HIGHWAY  ENGINEERING 

SECTION  II 

USE  AND  TRAFFIC 
Sixth  Communication 

ROAD  SIGNS.    MEASURES  TAKEN  TO  CARRY  OUT  THE 
RESOLUTIONS  OF  THE  PARIS  CONGRESS 

Austria 

31.  BRADACZEK,  THEODOR,  Imperial   Commissioner  of 
Public  Works,  Prague.     Road  signs.     Erection  and 
equipment  of  sign  posts.     Application  of  road  mark- 
ings and  number  of  notice  boards  required  on  the 
public  roads  in  the  Kingdom  of  Bohemia. 

Belgium 

32.  VAN  ZEEBROECK,  ED.,  Delegate  of  the  Touring  Club 
of  Belgium,  Brussels; 

COLARD,  H.,  Delegate  of  the  Touring  Club  of  Belgium, 

Brussels; 

FOURMANOIS,   A.,  Delegate  of  the  Touring  Club  of 

Belgium,  Brussels;    and 

VAN  MEERBEECK,  H.,  Delegate  of  the  Touring  Club 

of  Belgium,   Brussels.     The  conventional  sign  on 

the  caution  sign  post. 

France 

33.  CHAIX,    EDMOND,    President,     Touring    Committee, 
Automobile    Club    of  France,    Paris.     Road    signs. 
Measures  taken  to   carry  out  the  resolutions  of 
the   Paris   Congress.     Resolutions   passed   by   the 
International   Meeting  of  Touring   Societies   held 
on  December  1st,  1908,  and  by  the  International 
Diplomatic  Conference  held  on  October  8th,  1909. 


THE    CONGRESS  25 

Hungary 

34.  NEMETHY,    JOSEF,    Royal    Chief   Engineer,    Zilah. 
Road    signs.     Kilometre    marking    of    the    roads; 
information  in  regard  to  direction,  distances,  heights, 
obstacles  and  dangerous  places. 

Italy 

35.  TOLLER,   GINO,   Engineer,   Milan.     Sign    posts    of 
the  Touring  Club  of  Italy. 

Netherlands 

36.  Pos,  G.  A.,  Vice-President,  Touring  Club  of  Nether- 
lands,   Baarn.     Road    signs.     Measures    taken    to 
enact  the  resolution  of  the  International  Conference 
held  on  December  1st,  1908. 

Seventh  Communication 

VARIOUS  KINDS  OF  SOFT  TIRES:    USE,  ADVANTAGES, 
DISADVANTAGES,  ETC. 

Belgium 

37.  HANSEZ,    JULES,    President,     Touring     Committee, 
Royal  Automobile  Club,  Brussels.     Different  kinds 
of   flexible  tires.     Use,  advantages   and  disadvan- 
tages. 

France 

38.  FERRUS,    COMMANDANT    L.,    Member,    Automobile 
Club  of  France.     History  of  the  various  kinds  of 
tires.     Use,  advantages  and  disadvantages. 

France 

38.  bis.  BAUDRY  DE  SAUNIER,  L.,  Member,  Automobile 
Club  of  France.  Necessity  of  elastic  tires  for 
rapidly  moving  vehicles.  Pneumatic  tires. 


26  HIGHWAY   ENGINEERING 

Italy 

39.  ARISI,  T.,  Engineer,  Member,  Automobile    Club   of 
Italy.     Different  kinds  of  resilient  tires. 

Eighth  Communication 

CENSUS  OF  TRAFFIC  AND  TONNAGE.  METHODS  IN 
USE  AND  RESULTS  OBTAINED.  UNITS  ADOPTED 

Bulgaria 

40.  GUECHOFF,  STEFAN  CHR.,  Director-General  of  High- 
ways, Sofia.     Census  of  traffic  and  tonnage  hitherto 
carried  out  in  Bulgaria. 

France 

41.  MOULLE,    A.,    Chief,    Division    of   Highways     and 
Bridges,  Ministry  of  Public  Works,  Paris.     Census 
of  traffic  on  the  National  Roads  of  France. 

Italy 

42.  VANDONE,    ITALO,     Chief    Engineer,     Province     of 
Milan.     Various  censuses  of  the  number  of  vehicles 
and  of  the  tonnage  in  some  provinces  of  Italy. 

All  the  reports  and  communications  were  distributed 
to  the  members  of  the  Congress  many  weeks  previous  to 
the  opening  of  the  Congress  at  Brussels.  The  papers  were 
printed  in  the  three  official  languages:  English,  French  and 
German. 

The  Executive  Bureau  had  appointed  for  each  question 
a  general  reporter  who  reviewed  all  the  reports  submitted 
relative  to  the  assigned  question  and  formulated  conclusions 
which  were  based  to  a  great  extent  upon  the  recommenda- 
tions of  the  various  reporters.  The  general  reports  on  the 


THE    CONGRESS  27 

nine  questions  were  bound  together  and  distributed  to 
the  members  on  the  first  day  of  the  Congress. 

The  Congress  was  divided  into  two  sections  with  a 
further  sub-division  of  Section  I  into  sub-sections  A  and 
B.  A  total  of  eleven  sectional  meetings  were  held.  The 
technical  sessions  were  devoted  to  the  consideration  of 
the  tentative  conclusions  which  were  proposed  by  the 
general  reporters  relative  to  the  various  questions,  and  the 
adoption  of  conclusions  which  would  be  submitted  to  a 
general  meeting  of  the  Congress. 

The  proceedings  of  the  various  sessions  were  carried 
on  in  the  three  official  languages  of  the  Congress,  English, 
French  and  German;  that  is,  after  a  discussion  had  been 
given  in  one  language,  a  digest  of  the  same  was  immediately 
given  in  the  other  two  languages.  The  English-speaking 
members  of  the  Congress,  besides  taking  an  active  part  in 
the  regular  meetings,  also  met  at  various  times  for  the 
discussion  of  the  tentative  conclusions  and  the  consideration 
of  other  subjects  of  mutual  interest. 

At  the  closing  session  of  the  Congress  held  on  Saturday, 
August  6th,  1910,  the  conclusions  given  in  Chapter  XXIV 
were  adopted  without  discussion. 


28 


HIGHWAY   ENGINEERING 


CLASSIFICATION  OF  MEMBERS   OF  THE  SECOND  INTERNATIONAL 
ROAD  CONGRESS 


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Total  Number  of 
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CHAPTER   II 

THE  EXHIBITION 

The  exhibition  of  road  machinery,  materials  and 
sections  of  roads  and  pavements  was  located  in  or  adjacent 
to  the  Palais  du  Genie  Civil  et  du  Congres  de  la  Route, 
which  was  situated  on  the  grounds  of  the  1910  Brussels 
International  Exposition. 

The  exhibit  designated  "The  History  of  the  Road"  was 
located  in  the  court  immediately  in  front  of  the  exhibition 
hall.  Thirteen  different  forms  of  construction  showing 
the  development  of  roads  and  pavements  from  the  time 
of  the  Roman  Empire  to  about  A.  D.  1800,  were  represented. 

Another  exhibit  of  interest  from  an  historical  point 
of  view  was  designated  "The  History  of  Paving  in  Paris. " 
Thirteen  different  forms  of  construction  were  represented 
in  this  exhibit,  the  period  covered  by  the  various  types 
dating  from  the  Gallic-Roman  period  to  modern  times. 
The  oldest  type  of  pavement  shown  in  this  exhibit  was  of 
Roman  construction  and  consisted  of  flagstones  set  in 
lime  concrete.  After  Roman  occupancy  and  through  the 
Middle  Ages,  the  streets  of  Paris  received  little  attention, 
many  of  them  becoming  little  better  than  open  sewers. 
The  development  of  stone  paving  is  shown  by  five  forms 
of  construction  in  the  exhibit,  the  first  being  crude  paving 
with  rough  stones,  the  second  being  constructed  with 
small  flagstones,  about  20  inches  or  24  inches  square  on 
the  top  face  and  about  7J/2  inches  in  depth,  the  third  being 
a  pavement  of  square  stone  blocks  about  8  inches  on  the 

29 


30  HIGHWAY   ENGINEERING 

side,  the  fourth  being  constructed  of  sharp  pointed  flint 
stones,  and  the  fifth  type  being  cubical  blocks  very  similar 
to  the  third  form.  Next  in  chronological  order  came  the 
metalling  proposed  by  Tresaguet,  and  still  later  Me  Adam's 
system  of  metalling.  The  remaining  four  types  exhibited 
were  of  modern  development,  there  being  two  forms  of 
modern  stone  block  pavement,  one  of  asphalt  pavement 
and  one  of  wood  block  pavement. 

In  the  form  of  a  circle  concentric  with  the  circle  formed 
by  the  exhibit  depicting  the  history  of  street  paving  in 
Paris,  was  an  interesting  exhibit  of  eleven  types  of  paving 
to  be  found  in  the  City  of  Brussels.  Four  systems  of 
stone  block  pavement  were  included  in  this  exhibit.  In 
two  of  these  pavements  tamped  sand  was  employed  for  a 
foundation,  while  the  foundation  of  a  third  was  of  broken 
brick  covered  by  a  thin  layer  of  sand.  A  fourth  type  of 
stone  block  pavement  had  its  joints  filled  with  bituminous 
material.  Two  types  of  metalling  were  represented  in 
this  exhibit,  the  system  of  Tresaguet  and  a  form  of  tar 
macadam.  Three  types  of  bituminous  pavement  com- 
pleted this  exhibit.  Two  of  these  pavements  were  of 
sheet  asphalt  construction,  one  of  them  being  the  so-called 
asphalt  comprime  composed  of  powdered  rock  asphalt 
and  the  other  being  constructed  of  sand  mixed  with  molten 
asphalt.  A  third  type  of  construction  employed  blocks 
composed  of  a  fine  mineral  aggregate  mixed  with  asphalt. 
There  was  also  included  in  this  exhibit  a  section  of  excellent 
wood  block  pavement  and  a  section  of  pavement  con- 
structed of  vitrified  brick  which  had  previously  been 
soaked  in  bituminous  material. 

A  fourth  group  constructed  in  the  form  of  a  semi-circle 
illustrated  the  history  of  the  development  of  the  cycling 


THE    EXHIBITION  31 

track.  The  forms  of  construction  represented  included 
a  cinder  track,  a  track  constructed  of  broken  brick  and 
cinders,  a  raised  metalled  track  with  cross-drain,  a  vitrified 
brick  track,  a  scoria  brick  track,  and  a  track  constructed 
of  porphyritic  slabs  from  Nieuport. 

Upon  one  side  of  the  street  leading  to  the  court  in 
front  of  the  exhibition  hall  was  an  extensive  exhibit  of 
modern  paving,  while  upon  the  opposite  side  was  an  equally 
extensive  exhibit  of  modern  forms  of  metalling.  The 
space  in  between  the  exhibition  surfaces  was  paved  with 
brick  by  the  Dutch  system.  'Vehicles  were  allowed  over 
the  entire  width  of  the  street,  it  being  possible,  therefore, 
to  observe  to  some  extent  the  adaptability  of  the  various 
surfaces  for  traffic  from  the  standpoints  of  noisiness  and 
slipperiness.  In  addition  to  the  above  exhibitions,  cross- 
sections  of  many  forms  of  construction  were  exhibited 
in  brick  boxes,  the  front  sides  of  which  were  of  glass.  These 
cross-sections  showed  the  detailed  construction  of  the  pave- 
ments from  the  subsoil  to  the  wearing  surface. 

An  excellent  opportunity  was  afforded  by  the  exhibit 
of  modern  paving  to  study  stone  block  pavements  from 
the  standpoint  of  desirable  size,  shape,  foundation  and 
material.  Four  sections  of  square  slabs,  about  6  inches  by 
4  inches  by  6  inches,  constructed  of  porphyry,  quartzite, 
granite  and  flint  were  laid  upon  sand  foundations.  Four 
sections  of  oblong  slabs,  about  4  inches  by  6J/2  inches  by  6 
inches,  of  the  same  materials  were  laid  on  foundations  of 
broken  stone  and  sand.  The  same  four  materials  in  the  form 
of  oblong  blocks,  5  inches  by  8  inches  by  6  inches,  were  also 
laid  on  concrete  foundations.  A  section  of  old  stone  blocks 
redressed  and  placed  on  a  concrete  foundation  formed  a 
part  of  this  exhibit.  One  section  of  stone  block  pavement 


32  HIGHWAY   ENGINEERING 

was  laid  upon  a  foundation  of  slabs  of  concrete.  Two 
sections  of  German  kleinpflaster  were,  perhaps,  the  most 
attractive  features  of  this  exhibit.  The  small  blocks 
composing  one  section  were  made  of  Swedish  granite, 
while  for  the  other  section  Riendotte  stone  was  employed. 
The  method  of  laying  these  small  blocks  in  arcs  adds  an 
oddly  artistic  appearance  to  kleinpflaster  pavements. 
The  two  remaining  sections  in  this  exhibit  were  a  pavement 
of  Straatklenkaart  bricks  and  a  section  of  the  Dernerbe 
system  of  metallic  trackways  for  paved  roads. 

The  exhibit  of  modern  systems  of  metalling  was  fully 
as  interesting  as  the  exhibit  of  modern  paving.  The  oldest 
method  represented  in  this  exhibit  was  Tresaguet's  system 
of  metalling,  employing  river  gravel  rolled  with  a  horse 
drawn  roller.  Ordinary  water  bound  macadam  of  quartz- 
ite  and  porphyry  mixed  and  also  of  porphyry  alone  were 
there  constructed,  while  the  use  of  slag  as  a  binder  was 
demonstrated  by  employing  it  as  a  binder  for  quartzite 
metalling.  Several  types  of  metalled  surfaces  bound  with 
bituminous  material  were  represented.  One  section  of 
metalling  upon  a  foundation  of  flat  rubble  was  treated  by 
the  penetration  method  with  tar.  Several  sections  built 
of  bituminous  macadam  by  the  mixing  method  were  upon 
exhibition.  Among  these  were  porphyry  which  had  been 
dipped  in  hot  tar,  chalk  which  had  been  dipped  in  hot  tar, 
and  the  English  method  of  employing  tarred  slag.  An  odd 
method  of  employing  bituminous  material,  known  as  the 
Rhouben  system  and  consisting  of  a  mixture  of  powdered 
tar-pitch,  small  stone,  steel  filings  and  cement,  was  also 
to  be  seen  in  this  exhibit. 

From  the  foregoing  brief  synopsis  of  exhibits  of  methods 
of  construction  it  is  apparent  that  an  excellent  opportunity 


THE    EXHIBITION  33 

was  afforded  to  observe  a  great  many  types  of  metalled  and 
paved  roads,  some  of  which  are  widely  known  and  others 
which  are  not  at  present  to  be  found  except  in  very  re- 
stricted localities. 

The  exhibits  of  road  machinery  were  extensive  and 
very  interesting,  since  the  types  of  machines  manufactured 
in  different  countries  were  congregated  and,  therefore,  could 
be  readily  compared.  Road  rollers,  crushing  plants, 
scarifiers,  bituminous  material  distributors,  road  sweepers 
and  sprinkling  carts,  and  many  kinds  of  small  tools  were 
well  represented.  A  very  interesting  exhibit  was  that  of 
a  complete  plant  employed  in  the  Aeberli  system  of  con- 
structing tar  macadam.  This  machine  cleans,  dries,  and 
passes  the  stone  through  a  bath  of  cold  tar.  Gasolene 
road  rollers  and  motor  street  sweepers  and  street  sprinklers 
were  shown  in  several  different  forms.  Many  companies 
dealing  in  road  building  materials  offered  exhibits  of  their 
products.  Notable  among  these  exhibits  were  those  of 
several  Belgium  stone  quarry  firms. 


CHAPTER  III 
THE  EXCURSIONS  AND  RECEPTIONS 

During  the  long  series  of  meetings  held  by  the  Congress 
a  number  of  excursions  and  receptions  were  participated 
in  by  members  of  the  Congress,  some  of  which  occasions 
were  social  in  character,  while  others  combined  pleasure 
with  an  investigation  of  methods  of  road  and  street  con- 
struction, quarries  and  other  civil  engineering  works. 
Some  very  brilliant  fetes  were  held  in  honor  of  the  Congress 
and  by  the  Congress. 

Two  excursions  were  made  upon  August  2nd,  one  party 
visiting  the  stone  quarries  of  Quenast  and  another  party 
visiting  the  quarries  at  Lessines.  The  party  journeying 
to  Quenast  was  met  at  the  station,  which  is  practically 
in  the  middle  of  the  quarry,  by  the  superintendent  of  the 
company  who  guided  the  visitors  about  the  works  and 
explained  the  methods  of  developing  the  quarry.  The 
chief  product  of  this  quarry  is  porphyry  stone  block  for 
paving  purposes.  The  works  in  the  valley  where  the  blocks 
are  finally  trimmed  were  visited  first.  The  sorting  and 
piling  of  the  blocks  by  size  also  takes  place  here.  After 
investigating  this  part  of  the  work  the  party  journeyed  to 
the  main  quarry,  which  is  connected  with  the  finishing 
works  in  the  valley  by  a  tunnel  about  400  feet  in  length. 
From  an  elevated  point  of  view  the  quarry  resembled  a 
huge  stone  amphitheatre  about  2,300  feet  in  circumference, 
the  various  stages  of  working  forming  very  regular  steps 
from  top  to  bottom.  About  three  thousand  workmen  are 

34 


THE    EXCURSIONS   AND   RECEPTIONS  35 

employed  in  this  quarry,  the  larger  part  of  them  being 
engaged  in  breaking  the  huge  pieces  of  stone  by  various 
means  to  sizes  suitable  for  paving  block.  The  rough 
blocks  are  taken  through  the  tunnel  in  cars  to  the  finishing 
works.  Perhaps  the  most  interesting  feature  of  the  quarry 
is  the  very  effective  and  economical  device  of  connecting 
the  different  stages  with  mechanically  hauled  trucks.  The 
trucks  are  carried  on  travellers  which  slide  along  rails 
which  are  nearly  vertical.  The  loaded  trucks,  as  they 
descend,  raise  the  empty  trucks.  The  party  visiting 
Lessines  was  met  by  representatives  of  the  municipality 
and  were  allowed  ample  opportunity  to  inspect  the  quar- 
ries situated  in  the  vicinity.  The  members  were  par- 
ticularly interested  in  studying  the  formation  of  the 
porphyrytic  diorite  of  the  quarries,  which  material  is  com- 
monly called  porphyry.  This  stone  occurs  in  funnel  shaped 
masses  varying  froni  160  feet  to  330  feet  in  depth.  The 
members  of  the  Congress  later  attended  a  banquet  given 
by  the  municipality  in  their  honor. 

Upon  August  6th  the  members  of  the  Congress  visited 
a  section  of  roadway  upon  the  Avenue  Tervueren  where 
experiments  with  the  "  Aeberli-Macadam "  system  were 
being  carried  out.  The  trip  was  somewhat  of  a  disappoint- 
ment because  the  inclement  weather  had  hindered  the 
work  to  such  an  extent  that  the  metalled  surface  had  net 
been  prepared.  An  opportunity  was  afforded,  however, 
to  study  the  method  of  preparing  the  foundation  for  the 
metalled  surface  and  also  to  inspect  the  machine  in  opera- 
tion which  is  used  in  this  method  to  coat  the  aggregate  with 
tar. 

The  excursion  to  the  quarries  of  Montfort  and  to  the 
City  of  Liege  upon  August  8th,  was  very  interesting.  The 


36  HIGHWAY   ENGINEERING 

quarries  were  operated  in  a  different  manner  from  the 
systems  employed  at  the  other  quarries  previously  visited 
by  members  of  the  Congress.  The  rough  stone  blocks 
hewed  out  in  the  quarry  are  lifted  by  means  of  windlasses 
up  inclined  planes  to  a  higher  level  where  workmen  finished 
the  blocks  under  extensive  thatched  roofs.  The  quarry  is 
near  the  water  front,  hence  the  finished  materials  are 
transported  largely  by  boat.  In  addition  to  stone  blocks 
the  company  deals  largely  in  broken  stone  for  metalled 
roads.  At  a  lunch  furnished  by  the  company  operating 
the  quarries  several  interesting  speeches  were  rendered. 
Mr.  Kleyer,  mayor  of  Liege,  attended  the  lunch  and  gave 
an  instructive  talk  upon  the  streets  of  that  city.  Sandstone 
sets  are  used  in  this  city  much  more  frequently  than  any 
other  type  of  pavement,  the  customary  foundation  being 
a  bed  of  concrete  5  inches  thick  covered  by  2f  inches  of 
sand.  This  type  of  pavement  is  costly,  but  Mr.  Kleyer 
stated  that  it  gave  very  satisfactory  results. 

The  excursion  to  the  Waterfalls  of  Coo,  to  Spa  and 
to  the  Gileppe  Dam,  upon  August  9th,  furnished  an  oppor- 
tunity for  the  members  to  inspect  two  unique  methods  of 
road  construction.  The  scenery  in  the  section  traversed, 
the  magnificent  spectacle  afforded  by  the  Waterfalls  of 
Coo,  and  the  imposing  character  of  the  huge  stone  dam  at 
the  Lake  of  Gileppe,  were  much  appreciated  by  the  party. 

The  last  excursion  upon  August  10th  to  the  Grottoes 
of  Han  and  the  Citadel  of  Namur  provided  an  opportunity 
to  inspect  an  experimental  section  of  the  road  on  the.  route 
from  Aywaille  to  Barvam. 

In  addition  to  the  excursions  heretofore  mentioned, 
during  which  various  methods  of  road  and  pavement  con- 
struction were  observed,  there  were  two  trips  to  points 


THE    EXCURSIONS    AND    RECEPTIONS  37 

of  interest  which  were  undertaken  merely  for  pleasure. 
The  trip  to  Antwerp  upon  August  3rd  and  the  trip  to  the 
North  Sea  and  Ostend  up'on  August  5th  were  of  this  char- 
acter. Both  of  these  trips  were  extremely  pleasant  and 
added  greatly  to  the  enjoyment  of  the  Congress. 

Various  Belgium  municipalities  and  societies  very 
generously  offered  receptions  and  entertainments  to  the 
members  of  the  Congress.  The  first  of  these  occasions 
was  an  entertainment  upon  the  evening  of  July  31st,  by 
the  Touring  Club  of  Belgium,  consisting  of  an  excellent 
rendition  of  M.  Emile  Verhaeren's  drama,  "The  Cloister." 
The  following  morning  King  Albert  of  Belgium  received 
the  officers  of  the  Congress  at  the  Royal  Palace  and  dis- 
played considerable  interest  in  the  work  of  the  association. 
In  the  evening  the  Societe  Beige  des  Ingenieurs  et  des 
Industriels  furnished  a  musicale  for  the  enjoyment  of 
the  members  of  the  Congress.  An  excellent  program  was 
rendered  and  the  occasion  was  most  enjoyable.  Upon 
the  evening  of  August  3rd,  the  date  of  the  excursion  to 
Antwerp,  the  Minister  of  Public  Works  at  Antwerp  and 
the  Municipal  authorities  had  a  large  number  of  members 
of  the  Congress  as  guests  at  a  brilliant  reception.  The 
Congress  Banquet,  upon  the  evening  of  August  6th,'  was, 
perhaps,  the  most  enjoyable  occasion  of  this  nature  during 
the  entire  session.  The  affair  was  held  in  the  magnificent 
hall  of  the  "  Grande  Harmonie,"  and  was  well  attended. 
The  City  of  Brussels  was  not  lacking  in  hospitality,  an 
entertainment  being  offered  August  7th  by  the  Guild  of 
Burgomasters  and  Aldermen  of  the  City  of  Brussels.  The 
closing  banquet  of  the  Congress  was  held  on  the  evening  of 
August  10th  in  the  hall  of  the  Municipal  Theatre  of  Namur. 


Part  II 
TECHNICAL   DISCUSSIONS 


CHAPTER   IV 

ECONOMICS  OF  HIGHWAY  ENGINEERING 

BOULNOIS,  H.  PERCY,  M.  Inst.  C.  E.,  Deputy  Chief 
Engineer,  Local  Government  Board,  Whitehall,  London, 
S.  W.,  England,  Great  Britain. 

BREDTSCHNEIDER,  AUGUST,  Commissioner  of  Public 
Works,  Charlottenburg,  Germany. 

BRODIE,  JOHN  A.,  M.  Inst.  C.  E.,  City  Engineer,  Liver- 
pool, England,  Great  Britain. 

CATTANEO,  PAOLO,  Engineer,  Office  of  Municipal  En- 
gineer, Milan,  Italy. 

CROMPTON,  COL.  R.  E.,  M.  Inst.  C.  E.,  Royal  Automobile 
Club,  London,  England,  Great  Britain. 

EISENLOHR,  Director,  Board  of  Public  Works,  Strasburg, 
Germany. 

FLECK,  GEORG,  Commissioner,  Board  of  Public  Works, 
Dresden,  Germany. 

FLETCHER,  AUSTIN  B.,  M.  Am.  Soc.  C.  E.,  Secretary, 
Massachusetts  Highway  Commission,  Boston,  Mass.,  U.  S.  A. 

FORESTIER,  J.  C.  N.,  Superintendent,  Eastern  Division 
of  Parkways,  Paris,  France. 

38 


ECONOMICS    OF    HIGHWAY   ENGINEERING  39 

FROIDURE,  EUGENE,  Principal  Engineer  of  Bridges  and 
Roads,  Ypres,  Belgium. 

HOOKER,  S.  PERCY,  Chairman,  New  York  Highway 
Commission,  Albany,  N.  Y.,  U.  S.  A. 

HORBURGER,  Member,  Board  of  Public  Works,  Munich, 
Germany. 

LAFARGA,  PROSPERO,  Engineer  of  Highways,  Canals  and 
Harbors,  Alicante,  Spain. 

LE  GAVRIAN,  P.,  Engineer  of  Bridges  and  Roads,  Ver- 
sailles, France. 

LEWIS,  NELSON  P.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer, 
Board  of  Estimate  and  Apportionment,  New  York,  N.  Y., 
U.  S.  A. 

LLOYD  DAVIES,  D.  E.,  M.  Inst.  C.  E.,  Chief  Engineer 
to  the  Municipality  of  Alexandria,  Egypt. 

MAZEROLLE,  L.,  Engineer  of  Bridges  and  Roads,  Paris, 
France. 

SMITH,  J.  WALKER,  M.  Inst.  C.  E.,  City  Engineer, 
Edinburgh,  Scotland,  Great  Britain. 

VERSTRAETE,  RICHARD,  Engineer  of  Bridges  and  Roads, 
Bruges,  Belgium. 

Belgium.  EUGENE  FROIDURE,  and  RICHARD  VER- 
STRAETE. The  nature  of  the  binding  materials  to  be 
employed  in  road  construction  depends  upon  climatic  condi- 
tions. In  rainy  districts  sand,  fine  river  gravel,  and  granula- 
ted porphyry,  quartz  or  hard  sandstone,  may  be  used.  In  dry, 
hot  districts  a  binding  material  must  not  powder,  melt  or 
soften.  In  regions  of  severe  cold,  heavy  sands,  granulated 


40  HIGHWAY   ENGINEERING 

sandstone,  porphyry  or  quartz,  a  slow  binding  mortar  of  sand 
and  cement,  and  granulated  slag-mortar  may  be  used.  In 
windy  districts  materials  must  be  adherent  like  clay,  tar, 
or  various  mortars  of  cement  and  lime. 

Egypt.  D.  E.  LLOYD  DAVIES.  The  climate  of  North- 
ern Egypt  is  very  favorable  to  road  construction  because 
of  its  small  rainfall  and  absence  from  frost.  That  the  roads 
are  practically  dustless,  notwithstanding  a  prevalent 
strong  northerly  sea  breeze,  demonstrates  the  success  of  the 
systems  adopted.  Asphalt  is  used  for  the  best  business 
quarters,  volcanic  slag  stone  pavement  for  heavy  commercial 
traffic,  and  tar  painted  macadam  for  the  main  country  and 
suburban  roads.  The  construction  of  compressed  asphalt 
pavements  does  not  differ  materially  from  the  practice  in 
the  majority  of  European  cities. 

Urine  readily  attacks  the  asphalt  surface  and  must 
not  be  allowed  to  accumulate  or  to  remain  stagnant  for  any 
length  of  time,  but  with  adequate  drainage  and  careful 
cleansing,  this  disadvantage  need  not  be  taken  into  con- 
sideration. On  iron  bridges  and  other  structures  subject 
to  vibration,  ordinary  compressed  asphalt  fails  to  give 
good  results.  The  author  has  overcome  this  difficulty  by 
substituting  asphalt  blocks,  subjected  to  a  pressure  of 
8,532  pounds  per  square  inch,  and  laid  on  bituminous 
concrete  in  proportions  of  58  per  cent  of  mastic  asphalt  to 
45  per  cent  of  silicious  stone. 

At  Alexandria  experiments  with  rock  asphalt  paving 
have  been  carried  out.  The  rock  asphalt  was  crushed  to 
pass  through  a  4  inch  screen  and  laid  4f  inches  thick  on  a 
concrete  or  old  macadam  base.  The  surface  was  then 
rolled  with  a  roller  weighing  between  8  and  10  tons.  The 
final  thickness  of  the  surfacing  was  3J  inches.  The  result- 


ECONOMICS    OF    HIGHWAY   ENGINEERING  41 

ing  pavement  showed  no  signs  of  deterioration  at  the  end 
of  two  years,  was  more  elastic  than  compressed  asphalt, 
and  furnished  a  better  foothold  for  horses. 

France.  J.  C.  N.  FORESTIER.  The  attention  of  the 
Congress  of  1908  was  called  to  the  harmful  effect  of  tar  on 
plants  and  trees.  At  that  time  it  was  considered  especially 
a  question  of  the  action  on  plants  used  for  floral  decoration, 
because  the  cellular  tissue  of  such  plants  is  tender.  It 
seemed  logical  to  expect  that  the  same  effects  would  be  felt 
in  course  of  time  by  shrubs  and  trees,  which  are  more 
resistant,  and  later  experience  has  proved  that  the  harm 
done  to  this  type  of  vegetation  is  unfortunately  very  great. 
The  writer  particularly  points  to  the  Avenue  du  Bois  de 
Boulogne  where  the  formerly  most  beautiful  trees  are  now 
all  or  nearly  all  in  such  a  condition  that  fear  is  being  en- 
tertained of  not  being  able  to  effect  their  recovery  and 
preservation. 

At  what  period  and  how  does  the  tar  act?  The  first 
harmful  and  often  very  rapid  effect  takes  place  at  the  time 
of  spreading  the  hot  tar.  On  two  occasions  in  different 
years  on  the  Boulevard  Lannes,  at  Paris,  a  border  bed  of 
sedium  spurium  has  turned  brown  on  the  same  day  that 
tarring  was  done  and  never  regreened.  The  sophoras  and 
the  lime  trees,  commencing  their  growth  in  spring,  have 
appeared  tainted  by  the  spreading  of  hot  tar  near  them, 
the  leaves  curling  and  appearing  to  be  stopped  in  their 
development.  In  order  to  avoid  this  disadvantage,  which, 
on  recurrence,  would  cause  the  death  of  the  plants,  it  is 
necessary  to  proceed  with  the  tarring  either  before  the 
commencement  of  the  growth  of  the  plants  along  the  roads, 
or  at  sufficiently  long  periods  afterwards. 

But  the  dangerous  action  of  the  tar  is  unfortunately 


42  HIGHWAY   ENGINEERING 

not  limited  to  the  vapours  of  its  most  volatile  constituent 
parts.  The  dust  raised  by  intense  traffic  deposits  itself 
on  the  plants  and,  with  the  slightest  sunshine,  burns  the 
leaves  and  buds,  and  stops  the  development  of  the  greater 
part  of  the  trees. 

The  trees  often  are  unaffected  the  first  and  second 
years,  they  show  fatigue  on  the  third  year,  and  on  the 
fourth  they  very  clearly  begin  to  die.  These  effects  are 
found  along  ways  of  intense  traffic,  such  as  the  Avenue  du 
Bois  de  Boulogne  at  Paris  and  the  Boulevard  Maillot  at 
Neuilly-sur-Seine,  where  in  spite  of  frequent  watering  the 
wear  of  the  road  surface  is  such,  and  the  traffic  so  intense, 
that  between  the  waterings  there  is  always  plenty  of  dust. 

France.  P.  LE  GAVRIAN.  Because  of  its  rapid  oxida- 
tion and  consequent  deterioration,  certain  French  engineers 
do  not  predict  a  great  future  for  tar  in  connection  with  its 
use  as  a  road  binder.  If  it  be  assumed  that  tar  perishes  in 
twelve  months  and  if  it  is  capable  of  lengthening  the  life 
of  a  road  by  the  same  period  of  time,  this  fact  would  be  of 
great  importance  on  roads  which  have  to  be  remade  regularly 
in  two,  three  or  four  years,  but  it  would  be  of  less  importance 
on  roads  subjected  to  little  wear  and  which  last  eight,  ten 
or  fifteen  years  when  untreated.  The  uncertainty  attend- 
ing the  use  of  tar  on  roads  draws  attention  to  the  asphaltic 
products  which  are  of  more  stable  character,  and  with 
which  it  may  be  hoped,  even  with  a  doubtless  enhanced  first 
cost,  more  complete  and  more  reliable  results  may  be  ob- 
tained. 

France.  L.  MAZEROLLE.  The  choice  of  surfacing 
materials  to  be  adopted  for  the  roadways  of  a  large  city 
depends  on  a  number  of  considerations,  the  problem  being 
all  the  more  complex,  since  the  choice  may  concern  materials 


ECONOMICS    OF    HIGHWAY   ENGINEERING  43 

of  very  varied  natures,  and,  since  the  number  of  cases 
where  the  advantages  and  disadvantages  of  the  methods 
in  use  appear  to  contradict  one  another  are  very  frequent. 
We  should  not,  therefore,  attempt  to  fix  invariable  rules 
leading  to  mathematical  conclusions. 

The  cost  of  construction  and  maintenance  is  not  usually, 
in  large  cities,  the  determining  factor  which  influences  the 
selection  of  surfacing  materials.  In  Paris  the  unit  costs  of 
maintenance  of  macadam,  asphalt  pavement,  wood  pave- 
ment, and  stone  block  pavement  are  relatively  in  the  order 
here  given,  macadam  being  the  most  costly  and  stone  block 
pavement  being  the  least  costly.  The  actual  cost  of  main- 
tenance for  a  given  surface  is  difficult  to  state  because  of 
the  varying  standards  of  excellence  in  the  surface  which 
different  localities  intend  to  maintain. 

The  nature  of  the  traffic  is  of  prime  importance  in  the 
maintenance  of  the  roads,  and  it  would  be  very  interesting 
to  be  able  to  represent  it  in  figures  proportional  to  its 
destructive  character. 

Noiselessness  is  an  essential  consideration  in  connection 
with  city  streets,  especially  in  the  vicinity  of  schools, 
hospitals  and  other  public  buildings.  Macadam  and  wood 
pavement  have  very  nearly  the  same  degree  of  noisiness. 
Stone  block  pavement  is  the  noisiest  type  of  pavement. 
On  asphalt  pavements  the  noise  of  wheels  is  insignificant 
compared  to  the  noise  from  horses'  hoofs. 

It  is  necessary  to  distinguish  between  the  transported 
dust  due  to  horse  droppings,  to  earth  and  gravel  escaping 
from  carts,  to  building  construction,  to  mud  carried  along 
by  traffic,  to  refuse  from  riparian  dwellers  or  the  passers-by, 
etc.,  and  the  dust  due  to  the  wear  of  the  roadway  or  from 
the  repairs  required  for  its  maintenance.  The  nature  of 


44  HIGHWAY   ENGINEERING 

the  road  surface  will  obviously  have  no  influence  on  the 
dust  arising  from  the  causes  of  the  first  category,  but  the 
road  surface  on  the  other  hand  has  to  accommodate  itself 
to  the  influences  of  dust.  Only  wood  pavement  appears 
somewhat  affected  in  this  respect,  a  faulty  cleansing  and  a 
prolonged  contact  of  mud  with  it  being  disastrous.  Maca- 
dam roads  have  the  greatest  tendency  to  produce  dust. 
Next  in  order  come  stone  block  pavements.  Wood  pave- 
ments and  asphalt  pavements  produce  in  themselves  little 
dust,  but  the  application  of  sand  or  gravel  to  prevent  slip- 
periness  in  wet  weather  often  creates  a  source  of  dust. 

Slipperiness  is  much  more  to  be  feared  when  the  sur- 
face is  smooth  and  in  consequence  more  perfect  in  regard 
to  other  features.  The  chances  of  slipping  increase  with 
the  gradient  in  such  a  manner  that  slipperiness  and  gradient 
should  be  simultaneously  examined.  Compressed  asphalt 
is  apt  to  become  slippery,  especially  in  wet  weather.  When 
the  slope  of  a  road  exceeds  1.5  per  cent,  asphalt  is  not 
used.  Some  kinds  of  stone  are  slippery  when  made  into 
stone  blocks,  porphyry  having  been  given  up  in  Paris  for 
this  reason.  Wood  pavement  is  not  slippery  when  it  is 
clean.  In  Paris  wood  blocks  are  used  on  gradients  up  to 
5  per  cent. 

It  is  essential  to  be  able  to  repair  a  road  surface  without 
causing  too  great  a  nuisance  to  traffic.  In  the  case  of 
macadam  roads,  Paris  is  gradually  giving  up  the  system 
of  maintenance  called  partial  repairs  for  the  more  satisfac- 
tory method  of  complete  resurfacing.  It  is  considered  a 
better  scheme  to  block  the  road  a  few  days  entirely  rather 
than  to  make  poor  repairs.  Stone  block  pavements  are 
readily  repaired  without  delay,  while  the  repair  of  wood 
block  pavements  necessitates  a  slight  delay  in  order  to  allow 


ECONOMICS    OF    HIGHWAY   ENGINEERING  45 

the  cement  in  the  joints  time  to  set.  Where  it  is  especially 
desired  to  reduce  the  delay  incident  to  repair  of  wood  block 
pavements,  a  heavy  coat  of  sand  is  put  on  to  deaden  the 
shock,  but  this  method  is  not  very  satisfactory. 

Experiments  have  shown  that  all  rails  of  tramways 
undergo  a  deflection  upon  the  passage  of  tramcars.  Hence 
a  separation  between  rail  and  road  surface  is  inevitable. 
The  tendency  of  vehicles  to  keep  two  wheels  on  a  track  is 
injurious  in  disturbing  the  surface  close  to  the  rail  and  also 
in  forming  a  path  the  width  of  the  gauge  of  the  vehicles 
from  the  rails.  Stone  metalling  is  altogether  unacceptable 
for  the  rail  areas  of  urban  tramways.  Asphalt  pavement 
proves  unsatisfactory  next  to  the  rails,  and  repairs  are 
costly.  The  experiment  of  placing  an  elastic  layer  of 
poured  bitumen  between  the  rail  and  the  asphalt  has  not 
been  found  satisfactory.  Wood  pavement  gives  very  good 
results  next  to  rails  where  the  rails  are  on  a  firm  concrete 
base.  The  maintenance,  however,  is  rather  costly,  especi- 
ally when  the  wood  has  to  be  freed  from  sap  in  order  to 
remedy  the  nuisance  arising  from  creeping.  Stone  block 
pavement  seems  to  suffer  least  next  to  rails,  but  this  is  due 
in  part  to  the  fact  that  the  surface  is  naturally  rather 
irregular  and  the  public  is  consequently  less  exacting  with 
regard  to  it. 

From  the  point  of  view  of  hygiene  the  best  road  sur- 
facing material  is  the  one  which,  having  no  joints  whatever, 
does  not  absorb  the  liquids  falling  on  the  roadway.  Com- 
pressed asphalt  is  theoretically  the  best  road  surfacing 
from  this  standpoint.  Stone  block  pavements  seem  subject 
to  criticism  because  of  the  apparent  infiltration  of  water 
through  the  sand  joints.  This  infiltration  is  frequently 
found  very  slight  where  old  pavements  are  removed.  Wood 


46  HIGHWAY   ENGINEERING 

pavements  are  often  accused  of  absorbing  filthy  liquids, 
but  experiments  carried  out  at  Paris  refute  this  theory. 
Altogether  it  appears  that  public  health  is  less  affected 
by  the  nature  of  the  material  constituting  the  road  surface 
than  by  the  quantity  of  dust  produced  and  by  the  extent 
to  which  cleaning  operations  are  carried  out. 

On  roads  in  good  state  of  repair  the  resistance  to  wheels 
appears  to  be  very  little  dependent  upon  the  nature  of  the 
road  surface.  This  doubtless  explains  why,  since  the 
celebrated  experiments  of  General  Morin,  the  question  has 
been  relatively  little  studied,  at  least  in  France. 

Macadam  costs  between  $1.13  and  $1.45  per  square 
yard  according  to  whether  millstone  grit  or  porphyry  is 
used.  The  cost  of  maintenance  reaches  36  cents  per  year 
in  certain  instances.  Tar  treatment  of  macadam  roads 
has  increased  very  extensively  in  recent  years,  the  labor 
being  done  by  city  workmen  at  a  cost  of  about  2*/£  cents 
per  square  yard.  The  tar  treatment  of  roads  has,  on  some 
streets  with  heavy  traffic,  lasted  only  a  very  short  time, 
while  in  other  cases  better  results  have  been  secured.  In 
spite  of  the  recent  improvements  in  macadam  construction, 
it  seems  that,  from  all  points  of  view,  macadamizing  should 
not  be  prescribed  for  urban  roads  of  any  importance. 

The  first  cost  of  construction  of  a  square  yard  of  stone 
block  pavement  varies  between  $2.83  and  $3.53.  The 
maintenance  is  about  13  cents  per  square  yard  per  year. 
Laying  the  blocks  directly  on  concrete  has  been  given  up 
because  of  the  lack  of  elasticity.  Trials  with  cement  or 
tar  in  the  joints  have  not  been  developed.  The  rolling  of 
stone  blocks  has  been  tried  and  found  inferior  to  tamping 
by  an  experienced  paver.  The  chief  fault  of  stone 
block  pavement  is  its  noise,  and  it  is  for  this  reason 


ECONOMICS    OF    HIGHWAY   ENGINEERING  47 

that  it  is  disappearing  on  all  first  class  streets  with 
intense  traffic. 

The  average  cost  of  constructing  a  square  yard  of 
asphalt  pavement  2  inches  thick  is  from  $2.87  to  $3.18, 
including  the  concrete  foundations.  The  Rogusa  rock 
(Sicily),  Val  de  Travers,  Seyssel,  and  lately  Saint  Jean  de 
Maruejol  rock  have  been  used.  No  precise  rule  appears 
to  exist  relative  to  the  choice  of  powder  and  the  proportion 
of  bitumen  dependent  upon  the  position  of  the  street,  in 
spite  of  the  importance  which  is  attached  to  these  precau- 
tions in  other  countries.  American  asphalt,  a  mixture  of 
silicious  sand  and  bitumen,  has  been  tried  and  has  proved 
satisfactory.  It  appears  less  slippery  and  less  liable  to 
peel.  Asphalt  macadam  has  been  tried  in  several  places  in 
Paris  with  varying  success. 

One  trial  of  asphalt  blocks  had  been  attempted,  and 
another  trial  was  about  to  be  undertaken  at  the  time  of 
writing  this  report.  The  elimination  of  the  transportation 
of  hot  powder  and  the  fact  that  no  compression  is  necessary 
recommended  this  form  of  paving  over  ordinary  asphalt 
pavements.  It  appears  on  account  of  its  brittleness,  how- 
ever, not  to  be  suitable  for  streets  of  excessively  heavy  traffic. 

The  first  cost  of  construction  of  a  square  yard  of  pave- 
ment of  wood,  including  the  foundation,  varies  according 
to  the  kind  of  roadway  from  $2.82  to  $3.06.  The  main- 
tenance may  be  kept  under  16  cents  per  square  yard  per 
annum. 

Germany.  AUGUST  BREDTSCHNEIDER;  HORBURGER; 
EISENLOHR;  and  GEORG  FLECK.  The  percentage  of 
macadam  surface  to  the  total  street  area  even  within  a 
city's  limits  varies  inversely  as  the  number  of  inhabitants. 
Macadam  surface  is  found  to  the  extent  of  44.9  per  cent  of 


48  HIGHWAY   ENGINEERING 

the  road  surface  in  some  small  towns,  while  in  Greater 
Berlin  only  2  per  cent  is  found.  This  form  of  surface  is 
the  cheapest  in  Germany  and  is  suitable  for  streets  of  light 
traffic. 

Great  Britain.  H.  PERCY  BOULNOIS.  In  England 
the  money  lent  by  the  Local  Government  Board  for  the 
construction  of  ordinary  macadam  roads  has  to  be  repaid 
in  five  years.  If,  however,  the  road  is  constructed  with 
tar  macadam,  the  term  of  repayment  is  extended  to  ten 
years,  which  shows  that  the  Board  considers  that  the  life 
of  the  road  is  doubled  by  the  adoption  of  this  type  of  con- 
struction. 

Great  Britain.  JOHN  A.  BRODIE.  The  writer  is  in 
charge  of  the  administration  of  a  number  of  roads  represent- 
ing the  most  varied  conditions,  and  his  personal  experience 
leads  him  to  this  deduction,  that  it  is  not  possible  to  condemn 
either  ordinary  macadam  or  macadam  constructed  with 
some  bituminous  material.  The  choice  of  surfacing  ma- 
terial is  not  so  much  a  question  of  whether  the  road  is 
located  within  or  without  the  city  as  it  is  a  question  of  the 
traffic.  If  the  traffic  is  very  slight  ordinary  macadam  or 
macadam  with  a  superficial  coat  of  tar  may  be  perfectly 
satisfactory:  with  a  traffic  of  80,000  tons  per  annum  per 
yard  of  width,  macadam  incorporated  with  a  bituminous 
material  gives  the  best  results,  especially  where  a  noiseless 
pavement  is  desired;  in  the  case  of  a  traffic  up  to  400,000 
tons  per  annum  per  yard  of  width,  stone  block  pavement 
of  the  very  best  quality  is  necessary.  It  is,  therefore,  de- 
sirable to  subdivide  the  streets  into  ciasses  according  to 
their  traffic. 

Great  Britain.  COL.  R.  E.  CROMPTON.  It  has  been 
only  within  a  few  years  that  macadam  roads  have 


ECONOMICS   OF   HIGHWAY   ENGINEERING  49 

given  satisfaction  in  England.  The  development  of 
tarring  is  responsible  for  this  new  status  of  the  macadam 
surface. 

To  insure  success  in  any  tarring  operation  it  is  necessary 
to  adopt  the  following  precautions:  a  careful  selection  of 
the  bituminous  material;  a  careful  study  of  the  road  metal 
as  to  its  capacity  to  absorb  the  tar;  a  study  of  the  heat 
radiating  properties  of  the  road  materials,  as  affecting  the 
deposition  of  hoar  frost  on  the  surface  and  consequent 
slipperiness;  and  finally  the  application  of  the  minimum 
quantity  of  tar  which  will  effectually  waterproof  the  surface, 
an  excess  of  tar  remaining  fluid  within  the  road  allowing 
by  its  lubricating  action  the  movement  of  the  stones 
among  themselves. 

In  London  and  Liverpool  stone  block  pavement  is  only 
adopted  for  streets  in  the  vicinity  of  the  docks  where  the 
traffic  attains  a  million  tons  per  annum  per  yard  width  of 
roadway.  For  some  time,  however,  a  more  silent  and 
elastic  form  of  surfacing,  obtained  by  the  use  of  some 
bituminous  material  with  broken  stone,  has  been  substituted 
for  stone  block  pavement  in  many  places. 

Great  Britain.  J.  WALKER  SMITH.  The  method  of 
construction  to  be  employed  depends  upon  local  circum- 
stances. A  superficial  coat  of  tar  on  an  ordinary  macadam 
road  which  can  be  applied  at  a  cost  of  2  cents  per  square 
yard  may  be  satisfactory  under  certain  conditions.  On 
the  other  hand  conditions  may  require  the  construction  of 
a  bituminous  pavement  built  by  the  mixing  method  at  a 
cost  of  $1.25  per  square  yard.  There  are  several  methods 
of  construction,  the  cost  of  which  lies  between  2  cents  and 
$1.25  per  square  yard,  with  which  it  is  possible  to  meet 
almost  any  conditions. 


50  HIGHWAY   ENGINEERING 

Italy.  PAOLO  CATTANEO.  The  most  commonly  con- 
structed pavements  in  Italy  for  streets  of  very  heavy  traffic 
are  the  asphalt  pavement  and  the  stone  block  pavement. 

Stone  block  pavements  are  constructed  of  blocks  of 
granite,  porphyry,  syenite,  or  sandstone.  For  streets  of 
steep  gradient,  granite  is  the  most  suitable  material  because 
of  the  good  foothold  allowed.  As  was  stated  by  the  report- 
ing officers  from  Hungary  to  be  the  case  in  that  country, 
the  system  of  laying  the  blocks  diagonal  to  the  direction 
of  traffic  is  preferred  also  in  Italy.  Concrete  foundations 
are  not  extensively  used,  a  well  constructed  sand  foundation 
being  preferred. 

The  asphalt  used  for  the  construction  of  asphalt  pave- 
ment is  mined  in  Italy.  The  form  of  construction  is  the 
so-called  tamped  asphalt  pavement,  which  is  powdered  rock 
asphalt  heated  and  tamped  into  place. 

Wood  block  pavements  have  not  found  much  favor  in 
Italy. 

The  trials  made  in  Italy  with  tarring  macadam  surfaces 
or  with  tar  macadam  pavements  have  not  given  results 
favorable  enough  to  enable  one  to  recommend  the  adoption 
of  either  method  on  an  extensive  scale.  It  must  be  admitted, 
however,  that  a  great  stride  has  already  been  made  towards 
the  solution  of  the  dust  problem,  a  problem  which  is  of 
great  interest  to  all  who  study  sanitation  and  at  the  same 
time  questions  of  cost. 

Macadam  surfaces,  as  a  transitional  method,  are  cer- 
tainly appropriate  for  roads  in  towns  whose  financial  position 
does  not  allow  them  to  adopt  more  permanent  and  more 
expensive  systems. 

Spain.  PROSPERO  LAFARGA.  City  pavements  should 
possess  high  durability,  should  be  capable  of  being  repaired 


ECONOMICS   OF   HIGHWAY   ENGINEERING  51 

without  interfering  with  traffic  to  too  great  extent,  and 
should  not  be  excessively  productive  of  dust.  The  pollu- 
tion of  the  subsoil  is  an  important  element  to  be  considered 
in  those  towns  whose  sewers  are  in  poor  condition  as  regards 
.vmperviousness.  It  is  advisable  to  have  in  such  localities 
pavements  which  will  allow  the  escape  of  emanations  from 
the  subsoil. 

United  States.  AUSTIN  B.  FLETCHER.  In  Massa- 
chusetts it  is  estimated  that  the  maintenance  charge  of 
state  highways  has  increased  from  1.14  cents  to  5.7  cents 
per  square  yard  per  annum  in  the  last  three  years.  Al- 
though it  is  true  that  many  of  these  highways  were  nearing 
a  time  when  they  would  require  resurfacing,  this  need  for 
resurfacing  was  hastened  and  aggravated  by  the  motor 
vehicles.  An  estimate  made  before  motor  vehicles  became 
so  numerous  indicated  that  about  2.25  cents  per  square 
yard  per  annum  would  be  needed  for  the  proper  mainte- 
nance of  the  highways.  It  seems  fair  therefore  to  place  the 
bulk  of  this  extra  cost  on  the  increased  auto  traffic  and 
the  increased  speed  at  which  the  motor  vehicles  are  driven. 
From  1903  to  1909  the  number  of  motor  vehicles  registered 
in  Massachusetts  has  increased  from  3,241  to  23,902.  In 
1903  only  14  per  cent  of  the  motor  vehicles  were  more  than 
10  horse-power,  while  in  1908,  78  per  cent  were  in  excess 
of  10  horse-power. 

United  States.  S.  PERCY  HOOKER.  Patrol  sections 
five  to  eight  miles  in  length  have  been  established  by  the 
Commission.  Along  each  stretch  is  placed  a  pile  of  stone 
of  two  sizes,  %  inches  to  1J^  inches  and  1J4  inches  to  2J4 
inches.  Each  patrolman  supplies  a  horse  and  cart  and 
carries  a  barrel  of  water,  or  bituminous  material,  if  the  road 
has  been  treated  with  the  latter.  Whenever  a  rut  is  found 


52  HIGHWAY  ENGINEERING 

the  patrolman  fills  it  with  %  inch  stone.  It  has  been 
found  that  on  a  road  which  has  not  been  treated  with  a 
bituminous  material,  and  where  the  motor  traffic  does  not 
exceed  30  per  cent  of  the  entire  traffic,  that  the  average 
quantity  of  stone  used  by  the  patrolman  will  be  approxi- 
mately 25  cubic  yards  per  mile.  By  properly  repairing  the 
ruts  and  other  depressions  in  the  surface  and  by  the  constant 
brushing  back  of  the  screenings,  which  are  displaced  by  the 
traffic,  to  the  center  of  the  road,  it  has  been  possible  to 
maintain  many  of  the  ordinary  macadam  roads  in  an  ex- 
cellent condition. 

United  States.  NELSON  P.  LEWIS.  Two  years  ago 
the  writer  did  not  feel  disposed  to  plead  for  the  recognition 
of  macadam  as  a  suitable  material  for  anything  but  country 
roads,  or  possibly  for  little  used  and  unimportant  city  streets. 
During  the  two  years  which  have  elapsed  since  the  First 
Congress,  however,  there  has  been  a  great  improvement 
in  the  method  of  building  macadam  roads.  This  improve- 
ment, through  the  use  of  bituminous  binding  material,  has 
added  so  little  to  the  cost  of  this  kind  of  pavement  that  it 
still  remains  the  cheapest  form  of  road  surface  which  will 
meet  the  requirements  of  modern  traffic. 


CHAPTER  V 

TRAFFIC   CENSUS 

FLETCHER,  AUSTIN  B.,  M.  Am.  Soc.  C.  E.,  Secretary, 
Massachusetts  Highway  Commission,  Boston,  Mass.,  U.  S.  A. 

GUECHOFF,  STEFAN  CHR.,  Director-General  of  Highways, 
Sofia,  Bulgaria. 

MOULLE,  A.,  Chief,  Division  of  Highways  and  Bridges, 
Ministry  of  Public  Works,  Paris,  France. 

VANDONE,  ITALO,  Chief  Engineer,  Province  of  Milan, 
Italy. 

Bulgaria.  STEFAN  CHR.  GUECHOFF.  There  has  been 
but  one  traffic  census  carried  out  in  Bulgaria.  This  census 
was  taken  during  the  entire  year  from  Oct.  1st,  1896,  to 
Sept.  31st,  1897.  Observations  were  taken  on  a  length  of 
2,251  miles  of  National  Roads  at  208  posts.  Counting  was 
done  every  day  without  exception,  and  night  counting  was 
carried  on  each  night  at  some  posts,  on  all  but  rainy  nights 
at  others,  and  twice  each  week  on  different  nights  at  other 
posts. 

The  following  items  of  traffic  were  separately  noted: 
loaded  farm  wagons;  empty  farm  wagons  and  sundry  light 
vehicles;  loaded  beasts  of  burden;  unloaded  beasts  of  burden 
and  animals  with  riders;  large  cattle;  small  cattle.  As 
in  the  French  system,  a  unit  was  selected  for  the  reduction 
of  all  other  types  of  traffic.  Since  cattle  were  in  general 
use  as  draft  animals,  the  "yoke,"  a  wagon  drawn  by  a  yoke 

53 


54  HIGHWAY   ENGINEERING 

of  oxen,  was  chosen  as  this  unit.  Coefficients  of  reduction 
were  applied  to  each  category  of  traffic  and  the  total  result 
expressed  in  "yokes." 

The  gross  and  the  useful  tonnage  was  also  arrived  at 
by  estimates  of  the  weights  of  the  various  classes  of  traffic, 
an  estimate  easily  made  because  of  the  limited  nature  of  the 
kinds  of  traffic. 

The  writer  feels  confident  that  results  fully  as  satis- 
factory might  have  been  arrived  at  by  limiting  the  number 
of  observing  days  to  about  ten  days  in  each  quarter  of  the 
year. 

France.  A.  MOULLE.  Ten  censuses  of  traffic  over 
the  entire  country  have  been  undertaken  by  the  Depart- 
ment of  Bridges  and  Roads.  The  intervals  between  the 
taking  of  these  comprehensive  data  have  varied  from  five 
to  nine  years.  The  first  census  of  national  scope  was  taken 
in  1844,  although  previous  to  that  time  traffic  data  had  been 
collected  in  certain  localities.  Traffic  censuses  of  national 
character  will  in  the  future  be  undertaken  every  ten  years. 

Previous  to  the  advent  of  the  motor  car  the  categories 
of  traffic  noted  underwent  little  change.  Five  divisions 
were  recognized;  first,  freight  vehicles  and  those  for  agri- 
cultural purposes  when  loaded;  second,  public  vehicles 
for  common  transport  of  travellers  and  luggage;  third, 
empty  freight  or  agricultural  carts  and  private  carriages; 
fourth,  unharnessed  animals  of  large  size;  fifth,  light  live 
stock.  Until  the  census  of  1903  this  classification  was 
considered  sufficient,  but  the  increase  in  the  amount  of  motor 
car  traffic  necessitated  separate  classification  of  this  type 
of  vehicle.  Five  categories  are  here  also  recognized: 
first,  motor  vehicles  with  metal  tires,  which  are  usually 
heavily  loaded;  second,  motor  cycles;  third,  vehicles  with 


TRAFFIC    CENSUS  55 

elastic  tires  capable  of  travelling  thirty  miles  an  hour  and 
compelled  by  law  to  have  a  registration  number  attached; 
fourth,  vehicles  with  elastic  tires  which  cannot  attain  this 
speed;  fifth,  cycles. 

Coefficients  of  reduction  are  applied  to  each  division 
of  classification  of  both  groups  of  traffic  so  that  totals  may 
be  expressed  in  comparable  units.  The  unit  adopted  is 
known  as  a  "collar,"  and  is  described  as  a  traction  animal 
harnessed  to  a  loaded  vehicle.  The  coefficients  of  reduction 
employed  are  given  in  the  following  table : 

1.  Vehicles  loaded  with  produce  or  merchandise,  and  public 
conveyances  for  travellers 1 

2.  Empty  or  private  vehicles ^ 

3.  Unharnessed  animals Vz 

4.  Light  live  stock „ -^ 

Wt.  in  tons 

5.  Motor  cars  with  metal  tires  or  traction  engines — 0~284 — 

6.  Motor  cycle 0.3 

7.  Motor  car  with  number 3.0 

8.  Motor  car  without  number 1.0 

9.  Cycle 0.05 

The  tonnage  is  estimated  as  the  weight  transported. 
It  is  impossible  to  weigh  on  scales  all  the  different  types  of 
vehicles,  but  by  means  of  a  sufficiently  large  number  of 
actual  weighings,  and  information  gathered  from  the  princi- 
pal transport  agents,  the  average  weight  which  a  collar  of 
each  category  on  each  section  of  the  road  draws  is  ascer- 
tained. 

Tonnage  is  divided  into  "useful  tonnage"  and  "gross 
tonnage."  The  gross  tonnage  includes  everything  that  is 
drawn,  while  the  useful  tonnage  covers  only  the  load  carried 
by  the  vehicles.  The  weight  of  persons  was  in  the  earlier 
census  considered  as  useful  tonnage,  but,  since  1882,  this 
has  not  been  the  case. 


56  HIGHWAY   ENGINEERING 

The  importance  of  a  census  of  tramway  traffic  in  con- 
nection with  a  census  of  highway  traffic  has  been  recognized 
for  a  number  of  years.  The  usual  method  employed  is  to 
secure  such  data  from  the  companies  that  operate  the 
tramways.  It  has  been  recognized  that  the  influence 
exerted  by  the  tramways  on  the  wear  and  tear  of  roads  is 
in  no  wise  a  function  of  the  traffic  intensity,  but  that  it 
depends  more  especially  on  the  position  of  the  rails  in  the 
road  and  the  width  of  the  area  which  remains  entirely  free 
beyond  'the  rails  for  ordinary  traffic. 

The  census  is  taken  in  the  following  manner:  the 
roads  are  divided  into  a  certain  number  of  sections,  in  each  of 
which  it  is  assumed  that  the  traffic  is  more  or  less  constant 
from  one  end  to  the  other.  At  one  point  of  the  section, 
chosen  as  the  point  of  observation,  an  observer  notes  on  a 
printed  form  the  vehicles  and  animals  of  each  category 
which  pass  in  front  of  him.  The  choice  of  the  points  of 
observation  is  of  the  utmost  importance.  For  purposes  of 
comparison  of  the  censuses  it  is  essential  to  have  the  points 
of  observation  the  same  in  each  case  unless  changed  con- 
ditions make  it  absolutely  necessary  to  shift.  For  a  maxi- 
mum of  exactitude  it  would  be  necessary  to  divide  a  road 
into  as  many  sections  as  there  are  branch  roads,  but  this  is 
of  course  impracticable.  It  is  very  important  to  have 
conscientious  observers.  Roadmen  are  usually  employed 
for  the  purpose  in  France. 

The  census  is  taken  over  the  entire  year,  but  it  is  too 
expensive  to  take  it  each  day  in  the  year.  The  method 
considered  as  the  most  practicable,  from  the  standpoint  of 
the  elimination  of  undue  effect  of  abnormal  traffic  upon  the 
average  result,  is  to  take  count  upon  single  days  at  regular 
intervals.  The  last  two  censuses  have  been  taken  upon 


TRAFFIC    CENSUS  57 

single  days  at  a  constant  interval  of  thirteen  days.  Count- 
ing at  night  is  done  occasionally  upon  each  section  at  such 
times  as  the  engineer  sees  fit.  It  is  usually  desired  to  take  at 
least  one  night  count  in  each  of  the  four  seasons  of  the  year. 

Italy.  ITALO  VANDONE.  No  comprehensive  traffic 
census  over  the  entire  country  has  ever  been  taken.  The 
interest  in  the  matter  of  such  statistics  is  of  recent  develop- 
ment, although  isolated  instances  are  on  record  of  traffic 
data  having  been  secured  at  earlier  dates.  The  methods 
employed  in  the  various  provinces  vary  somewhat,  owing 
doubtless  to  variable  conditions. 

In  the  census  carried  out  near  Milan  sixty-three  posts 
were  established  at  thirteen  of  which  two  chief  roadmen 
observed  the  traffic,  by  day  and  by  night  without  interrup- 
tion, for  seven  consecutive  days  each  season,  or  for  twenty- 
eight  days  of  twenty-four  hours  in  the  year.  They  were 
provided  with  a  tent,  lanterns,  fires,  folding  chairs,  etc. 
At  the  other  fifty  posts  two  roadmen  were  placed,  generally 
those  of  the  nearest  road  district,  who  made  observations 
by  day  for  seven  consecutive  days  each  season,  or  for  twenty- 
eight  days  of  twelve  hours  in  the  year.  These  posts  were 
equipped  in  the  same  manner  as  above  mentioned.  The 
census  outside  Milan  extended  over  1908  and  1909. 

The  general  method  of  classification  and  reduction  to 
units  was  the  same  as  the  French  system,  the  French 
" collar"  being  employed,  although  the  coefficients  of 
reduction  varied  somewhat  from  the  French  usage. 

An  estimate  of  tonnage  was  secured  by  determining 
upon  the  average  weights  of  the  various  classifications  of 
traffic.  These  average  weights  were  secured  by  averaging 
frequent  observations  of  the  weights  of  various  types  of 
vehicles  by  the  observing  officers. 


58  HIGHWAY   ENGINEERING 

As  to  night  traffic,  the  writer  considers  that  the  ratio 
of  night  traffic  to  day  traffic  might  be  obtained  and  this 
ratio  applied  for  a  number  of  years  without  any  actual  night 
census  being  necessary. 

A  census  similar  to  the  one  at  Milan  was  carried  out 
in  the  province  of  Modena  from  1901  to  1904.  Each  year 
twenty-eight  observations  were  made,  one  being  taken  at 
each  station  every  thirteen  days.  Half  of  the  observations 
were  made  for  the  total  twenty-four  hours,  that  is,  once 
every  twenty-six  days.  There  were  two  overseers  at  every 
post  with  a  total  of  sixty-four  roadmen  and  twenty-four 
assistant  workmen. 

United  States.  AUSTIN  B.  FLETCHER.  A  traffic  census 
was  made  by  the  Commission  on  some  of  the  State  High- 
ways during  August  and  October,  1909.  Over  235  stations 
were  established  at  which  the  traffic  was  observed. 

The  following  table  shows  the  results  obtained: 

TOTAL  NUMBER  OF  VEHICLES  PER  DAY  OF  FOURTEEN  HOURS. 


HORSE  DRAWN 

AUTOMOBILE  * 

Total  all 

Light 

Heavy 

Total 

Runabouts 

Touring 

Total 

Kinds 

Cars 

August  

19,622 

17,969 

37,591 

5,922 

21,387 

27,309 

64,900 

October  

16,456 

17,967 

34,423 

3,995 

14,514 

18,509 

52,952 

AVERAGES  PER  DAY  PER  OBSERVER'S  STATION. 

HORSE  DRAWN  AUTOMOBILE*  Total  all 

Light  Heavy      Total  Runabouts  Touring       Total  Kinds 

Cars 

Aug.  (237 stations)..  83   76    159    25     90    115    274 
Oct.  (240 stations)..  69   75    144    17     60     77     221 


Motor  cycles  not  included. 


CHAPTER  VI 

MATERIALS  OF  HIGHWAY  ENGINEERING 

BREDTSCHNEIDER,  AUGUST,  Commissioner  of  Public 
Works,  Chariot  tenburg,  Germany. 

CAMERMAN,  EMILE,  Engineer,  Brussels,  Belgium. 

CORNU,  Louis,  Principal  Engineer  of  Bridges  and  Roads, 
Arlon,  Belgium. 

CROSBY,  WALTER  W.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer 
to  Maryland  Geological  and  Economic  Survey,  Baltimore, 
Maryland,  U.  S.  A. 

HENNING,  JOHN,  Imperial  Commissioner  of  Public 
Works,  Oberlahnstein-on-the-Rhine,  Germany. 

HUBBARD,  PREVOST,  Chemist,  Office  of  Public  Roads, 
Washington,  D.  C.,  U.  S.  A. 

LLOYD  DAVIES,  D.  E.,  M.  Inst.  C.  E.,  Chief  Engineer  to 
the  Municipality  of  Alexandria,  Egypt. 

MESNAGER,  AUGUSTIN,  Chief  Engineer  of  Bridges  and 
Roads,  Paris,  France. 

MIKHAILOFF,  PAUL,  Engineer  of  Highways,  St.  Peters- 
burg, Russia. 

TOURING  CLUB  OF  ITALY,  Italy. 

TSVETKOVSKY,  CONSTANTIN,  Engineer  of  Highways, 
Warsaw,  Russia. 

VAN  LOBEN  SELS,  M.  J.,  Vice-President,  Netherlands  As- 
sociation of  Brick  Manufacturers,  Nimwegen,  Netherlands. 

WALBAUM,  LUDWIG,  Imperial  Commissioner  of  Public 
Works,  Gratz,  Austria. 

59 


60  HIGHWAY   ENGINEERING 

Austria.  LUDWIG  WALBAUM.  Except  in  a  few  special 
cases  where  traffic  necessitates  paving,  the  roads  of  Styria 
are  macadamized.  The  material  usually  employed  is 
limestone,  although  graywacke,  serpentine,  horn-slate, 
eclogite,  trachyte  and  basaltic  rocks  are  also  used. 

The  stone  must  have  power  to  resist  abrasion,  should 
have  a  small  capacity  for  absorption  and  should  possess 
strong  binding  power.  The  tests  of  stone  in  Styria  are 
usually  confined  to  the  determination  of  absolute  strength, 
which  test  in  itself  often  gives  unsatisfactory  results. 

A  study  of  the  grain  of  material  for  ordinary  metalled 
roads  is  important  as  influencing  the  form  of  fracture.  A 
stone  whose  tendency  is  to  break  into  splinters  or  flat  slabs 
is  not  satisfactory.  Material  of  uniform  polygonal  form  is 
the  best  for  construction  work.  As  a  rule  stone  broken  by 
hand  gives  better  results  in  this  respect  than  stone  broken 
by  stone  crushers.  The  mechanical  methods  at  present 
employed  may  be  improved  to  secure  stone  of  better  quality. 
Owing  to  the  round  holes  in  a  crusher  screen,  long,  flat 
^stones  may  pass  through  readily.  The  writer  suggests 
the  use  of  a  secondary  screen  with  bars  of  triangular  cross- 
section  forming  long  slots  through  which  flat  stones  may 
pass  and  be  collected  in  a  separate  bin.  These  flat  stones 
may  be  recrushed  later  after  the  gauge  of  the  jaws  of  the 
crusher  has  been  narrowed. 

Belgium.  Louis  CORN.U  and  EMILE  CAMERMAN.  The 
top  course  of  a  macadamized  road  is  subjected  by  the  action 
of  wheels  to  crushing  forces,  to  internal  friction,  to  surface 
friction,  and  to  blows  more  or  less  severe  according  to  the 
unevenness  of  the  road.  The  action  of  horses'  hoofs  pro- 
duces friction  and  a  chipping  effect.  Owing  to  exposure 
on  the  surface  of  the  ground,  the  stone  is  subjected  to  frost 


MATERIALS    OF   HIGHWAY   ENGINEERING  61 

action  and  to  the  corroding  influence  of  rainwater  charged 
with   various   impurities   absorbed. 

In  order  to  resist  the  influences  mentioned  above  the 
stone  employed  should  be  tenacious,  elastic,  frost  proof,  only 
slightly  porous,  immune  from  attacks  of  acids  and  alkalies 
and  homogeneous.  In  order  to  satisfy  other  requirements 
not  mentioned  above  the  road  metal  should-not  be  capable 
of  receiving  a  polish  as  a  result  of  the  traffic.  It  would, 
therefore,  be  advisable  to  submit  the  materials  to  the 
following  tests  and  examinations  before  approval  is  given, 
if  it  is  desired  to  ascertain  to  what  extent  each  sample 
possesses  all  the  requisite  qualities: 

1.  Chemical   analysis,    qualitative   and    quantitative. 

2.  Resistance  to  compression. 

3.  Resistance  to  concussion. 

4.  Resistance  to  wear. 

5.  Resistance  to  alternate  freezing  and  thawing 

6.  Resistance  to  the  action  of  acid  solutions. 

7.  Resistance  to  the  action  of  alkaline  solutions. 

8.  Specific  gravity. 

9.  Porosity. 

10.  Amount  of  polish  in  wear. 

11.  Homogeneity. 

The  writer  is  of  the  opinion  that  it  is  not  possible, 
without  the  help  of  practical  experience,  to  make  a  judicious 
choice  of  materials  to  be  used  from  the  consideration  of  the 
results  of  laboratory  analysis.  The  investigation  of  old 
road  materials  to  see  whether  or  not  they  have  proved 
satisfactory  is  important.  The  same  tests  should  be  made 
of  the  old  materials  as  are  made  of  materials  to  be  used,  and 
in  addition  it  is  exceedingly  important  to  note  the  nature  of 


62  HIGHWAY   ENGINEERING 

traffic  over  the  road,  nature  of  soil,  the  climate,  conditions 
of  exposure,  gradient  of  the  road,  cross-section  of  the  road, 
original  dimensions  of  the  material  and  place  from  which 
the  material  originally  was  obtained.  It  is  also  important 
to  note  the  degree  of  satisfaction  the  road  has  given  from 
the  standpoint  of  slipperiness,  muddiness,  dustiness  and 
noisiness.  Information  as  to  the  amount  of  sweeping, 
watering,  tarring  and  scraping  employed  should  also  be 
secured. 

In  the  investigation  of  wood  blocks,  chemical  analysis 
is  valueless,  but  timber  should  be  examined  as  to  its  age 
when  felled,  its  texture,  its  compactness,  its  closeness  of 
grain,  its  general  soundness  and  such  physical  or  mechanical 
properties  of  wood  blocks  as  specific  gravity,  resistance  to 
frictional  wear,  resistance  to  crushing,  resistance  to  blows, 
elasticity,  and  hygroscopic  properties  should  be  ascertained. 

The  principal  qualities  which  rock  asphalt  for  asphalt 
pavements  should  possess  are  the  following: 

1.  Small  amount  of  sand,  as  this  substance  is  not  well 
adapted  to  compression. 

2.  Small  proportion  of  clay,  as  this  substance  is  apt  to 
cause  swelling  in  damp  weather  and  shrinkage  in  dry  weather. 

3.  Absence  of  pyrites,  a  substance  which  is  transformed 
by  heat  into  unstable  sulphides  which,  in  their  turn  by 
oxidation,    are   changed   into   soluble   sulphates   and   may 
cause  the  rapid  deterioration  of  the  surface. 

4.  The   asphalt   powder  used  in   making   compressed 
asphalt  should  contain  six  to  thirteen  per  cent  of  bitumen. 

5.  Homogeneity. 

All  of  these  qualities  except  the  last  can  be  verified  by 
chemical  analysis. 


MATERIALS   OF   HIGHWAY   ENGINEERING  63 

The  following  test  by  Durand  Claye  is  recommended  for 
detection  of  coal  tar  pitch  in  asphaltic  compounds:  the 
asphalt  is  well  broken  up  and  treated  with  carbon  bisulphide. 
The  liquid,  which  contains  the  dissolved  bituminous  matter, 
is  filtered  and  the  filtered  material  is  evaporated  until  all 
of  the  carbon  bisulphide  has  disappeared,  after  which  it 
is  heated  until  the  bituminous  mass  has  hardened.  This 
is  detached  from  the  bottom  of  the  receptacle  and  is  reduced 
to  fine  powder.  One-tenth  of  a  grain  of  this  powder  is 
treated  with  5  cubic  centimeters  of  concentrated  sulphuric 
acid  and  allowed  to  soak  for  twenty-four  hours.  Ten 
cubic  centimeters  of  water  are  then  carefully  added  and  the 
mixture  stirred.  The  water  is  allowed  to  act  for  some 
minutes  after  which  the  mixture  is  filtered  and  washed  with 
100  cubic  centimeters  of  water.  When  the  asphalt  is  pure, 
the  filtrate  is  colorless;  but  if  any  coal  tar  pitch  has  been 
added,  the  filtrate  will  vary  in  color  from  light  brown  to 
black,  according  to  the  amount  of  pitch  which  has  been 
added.  The  best  materials,  whose  use  may  be  tolerated 
in  order  to  add  fluidity  to  molten  asphalt,  are  Trinidad 
bitumen  and  the  fluid  pitch  of  mineral  oil.  They  should 
stand  the  following  test:  namely,  that  a  drop  allowed  to 
fall  on  blotting  paper  should  preserve  its  shape  without 
spreading  into  a  circular  patch,  even  in  three  days. 

Egypt.  D.  E.  LLOYD  DAVIES.  Macadam  road  con- 
struction in  Alexandria  has  been  very  successful,  the  stone 
used  being  basalt  of  the  middle  tertiary  age.  It  is  a  finely 
crystalline  volcanic  rock,  the  constituent  minerals  being 
chiefly  feldspar,  augite,  olivine  and  magnetite.  The  stone 
is  very  hard  and  tough,  and  great  difficulty  was  at  first 
experienced  in  finding  a  suitable  binding  material,  both 
silicious  and  calcareous  sand  proving  useless  for  the  purpose. 


64  HIGHWAY   ENGINEERING 

After  many  experiments  with  different  substances  the 
reddish  colored  earth  locally  known  as  tina  was  tried,  and 
the  result  was  so  favorable  that  it  has  been  universally 
adopted.  The  following  is  an  analysis  of  the  tina  kindly 
supplied  by  my  colleague,  Dr.  Dotschlich,  from  the  Chemical 
Department  of  the  Public  Health  Service: 

Sand 66.70  per  cent. 

Clay '.:..-...     9.98 

Humic  substances 1 . 23 

Earthy  carbonates  (calculated  as 

CaCO:) 17.31 

Water 3.50 

Soluble  substances  and  loss " .     1 . 28 

France.  AUGUSTIN  MESNAGER.  In  order  to  deter- 
mine the  resistance  of  stone  blocks  to  wear  by  friction  the 
general  practice  is  to  use  a  sanded  friction  plate.  The  sand 
for  this  use  is  obtained  by  crushing  a  quartz  sandstone  from 
a  certain  locality  and  screening  the  resulting  sand  to  a 
uniform  size.  The  plate,  loaded  with  250  grams  per  square 
yard  and  covered  uniformly  with  sand,  revolves  at  a  rate 
of  2,000  revolutions  per  hour.  Each  end  of  the  test  piece 
is  subjected  to  2,000  revolutions,  and  the  diminution  of 
height  at  each  end  is  measured. 

In  order  to  test  the  resistance  of  stone  blocks  to  blows 
of  horses'  hoofs  and  wheels  of  vehicles  the  Laboratory  of 
the  School  of  Bridges  and  Roads  employs  a  drop-weight 
machine.  A  weight  of  4.5  kilograms  falls  from  a  height  of 
1  meter  upon  a  cubical  specimen  of  4  centimeters  edge  length. 
The  number  of  times  the  weight  fails  to  create  complete 
fracture  is  an  indication  of  the  strength  of  the  block. 

The  only  test  for  metalling  material  which  will  be 


MATERIALS   OF   HIGHWAY   ENGINEERING  65 

described  is  the  test  for  resistance  to  internal  friction. 
This  experiment,  as  carried  out  at  the  Laboratory  of  the 
School  of  Bridges  and  Roads,  is  as  follows:  5  kilograms  of 
broken  stone  fragments,  selected  so  that  there  are  few  or 
no  sharp  edges,  are  placed  in  cylinders  which  are  revolved 
about  a  horizontal  axle  to  which  they  are  inclined  at  an 
angle  of  30  degrees.  The  cylinders  are  revolved  at  a  speed 
of  2,000  revolutions  per  hour  for  a  total  of  10,000  revolutions, 
and  the  dust  under  0.16  of  a  centimeter  in  diameter  is  care- 
fully collected  and  weighed.  The  coefficient  representing  the 

400 
quality  of  a  material  is  computed  by  the  formula  Q=  -jj- 

where  U  is  weight  in  grams  of  dust  under  0.16  of  a  centi- 
meter in  diameter  per  kilogram  of  material. 

Germany.  AUGUST  BREDTSCHNEIDER.  The  methods 
for  analyzing  rock  asphalt  as  employed  in  Germany,  are  as 
follows : 

A.  Analysis  of  the  asphalt  powder. 

1.  The  quantity  of  bitumen  soluble  in  chloroform  is 
found  by  pouring  chloroform  over  the  powder  until  there 
is  no  discoloration  of  the  liquid,  and  then  drying  and  weigh- 
ing the  residue  remaining. 

2.  The  insoluble  constituents  of  bitumen,  silica  and 
alumina  are  determined  by  pouring  hydrochloric  acid  over 
the   powder   left   from   test   number    1.     By   drying   and 
incinerating  this  powder  the  Si02  is  found.     The  difference 
in  weights  before  and  after  incineration  gives  the  quantity 
of  insoluble  bitumen.     By  rinding  the  percentage  of  ferric 
oxide    and    alumina    the  quantity  of  clay  may  be    cal- 
culated. 

3.  The  carbonate  of  lime  is  found  by  determining  the 


66  HIGHWAY   ENGINEERING 

quantity  of  carbonic  acid  (CO2),  formed  by  the  application 
of  hydrochloric  acid  to  the  asphalt. 

4.  The  specific  gravity  of  the  powder  is  found  by 
weighing  a  certain  volume  of  the  asphalt  powder  ten  times 
and  comparing  the  average  of  these  weights  with  the  weight 
of  the  same  volume  of  water. 

B.  Analysis  of  the  bitumen. 

1.  The  specific  gravity  is  determined  by  comparison 
with  the  weight  of  an  equal  volume  of  water. 

2.  The  melting  point  is  found  by  finding  the  tempera- 
ture at  which  a  sheet  of  bitumen  5  to  10  millimeters  in 
thickness  is  penetrated  by  5  grams  of  quicksilver. 

3.  The    dripping   point    is   found    by   measuring   the 
temperature  at  which  a  drop  falls  through  a  hole  3  milli- 
meters in  diameter  by  its  own  weight. 

4.  The  percentage  of  sulphur  is  determined  by  burning 
in  oxygen  and  measuring  the  quantity  of  sulphuric  acid 
formed.     From  this  percentage  the  percentage  of  sulphur 
may  be  computed. 

C.  Determination  of  geological  characteristics. 

Microscopic  tests  are  of  great  value  in  checking  state- 
ments by  manufacturers  as  to  the  origin  of  their  asphalts. 
Shells  and  other  animal  matter  present  may  readily  be 
discerned  by  examining  a  polished  sheet  of  asphalt  of  ex- 
treme thinness. 

Germany.  JOHN  HENNING.  We  have  used  in  Ger- 
many a  slag  which  contains  a  slight  quantity  of  silica  and 
xlime  and  which  is  a  product  of  the  lead  works  at  the  Lahn 
deposits.  This  slag  does  not  contain  40  per  cent  of  siliceous 


MATERIALS    OF   HIGHWAY   ENGINEERING  67 

and  lime  substances  as  does  that  of  blast  furnaces,  but  only 
16  to  20  per  cent  of  lime  and  28  to  30  per  cent  of  silicates. 
Its  other  constituents  are  35  to  40  per  cent  of  iron,  6  to  8 
per  cent  of  zinc  and  up  to  30  per  cent  of  sulphur.  The  effect 
of  sulphur  in  the  slag  is  harmful.  Compared  with  a  metal- 
ling of  tarred  basalt,  this  surfacing  of  tarred  lead  slag  is 
very  satisfactory. 

The  use  of  asphaltic  products,  oil  and  petroleum 
residues,  is  scarcely  known  at  all  in  Germany.  Coke  oven 
tar  which  is  extensively  produced  in  this  country  is  used 
almost  altogether  for  the  bituminous  material.  In  the 
construction  of  the  bituminous  pavements,  the  writer 
believes  that  preference  should  be  given  to  the  tar  which 
has  a  small  free  carbon  content. 

Italy.  TOURING  CLUB  OF  ITALY.  Although  labora- 
tory experiments  may  be  thought  indispensable  for  a  com- 
plete knowledge  of  metalling  materials,  they  are,  however,  not 
sufficient  to  define  the  coefficient  of  quality  of  such  material. 
Because  of  the  fact  that  laboratory  tests  are  made  separately 
for  each  cause  of  wear  they  cannot  reproduce  the  wear  and 
tear  on  a  highway  as  it  really  is  produced  by  the  principal 
causes  of  deterioration,  such  as  traffic,  atmospheric  effects, 
the  special  and  various  conditions  of  subsoil,  exposure, 
grade,  width  of  the  road,  etc. 

It  is  advisable  to  investigate  the  adaptability  of  various 
materials  of  predetermined  characteristics  for  various 
conditions  of  traffic  and  climate  by  employing  these  materials 
under  conditions  of  widely  differing  character  and  keeping 
accurate  records  of  the  adaptability  of  the  materials  in  each 
case. 

It  is  desirable  that  experiments  should  be  carried  out 
with  the  object  of  inventing  a  machine  capable  of  reproduc- 


68  HIGHWAY   ENGINEERING 

ing  in  a  laboratory  the  construction  of  an  artificial  macadam 
road  and  its  wear  and  tear  by  traffic.  If,  for  each  material 
thus  tried,  a  constant  relation  could  be  ascertained  between 
results  thus  obtained  and  those  obtained  by  comparative 
trials  on  the  highway  itself,  there  would  be  reason  to  attribute 
great  importance  to  the  results  obtained  by  this  machine 
in  estimating  the  coefficients  of  quality  of  metalling  ma- 
terial. 

It  will  be  well  to  study  whether  from  the  comparison 
of  the  results  of  different  laboratory  trials  with  those  of 
road  experiments  it  is  possible  to  deduce  a  synthetic  relation 
between  the  combination  of  the  physical,  chemical  and 
mechanical  properties  of  any  given  material  and  its  coefficient 
of  quality  determined  in  the  manner  described. 

Netherlands.  M.  J.  VAN  LOBEN  SELS.  The  gravel 
of  Holland  is  not  of  a  hard  nature.  The  roads  constructed 
with  gravel  have  a  tendency  to  rut  besides  being  very 
dusty  and  muddy.  By  building  a  track  of  brick  in  the 
centre  of  the  road  for  horses  to  tread  on  and  having  the 
remainder  of  the  road  gravel  gives  very  good  results. 

Nearly  two-thirds  of  the  State  Roads  are  built  of 
brick,  giving  excellent  results.  The  usual  dimensions  are 
approximately  2  inches  by  8J/2  inches.  In  South  Holland 
bricks  2  inches  by  3J/2  inches  by  7  inches  are  employed. 
Bricks  must  be  sound  to  prevent  chipping,  hard  to  resist 
horses'  hoofs,  not  deformed  in  any  way,  and  laid  on  a 
rolled  bed  of  sand. 

Russia.  PAUL  MIKHAILOFF,  and  CONSTANTIN  TSVET- 
KOVSKY.  Vitrified  bricks,  owing  to  lack  of  suitable  road 
metalling  materials,  and  the  excellent  results  attained,  are 
extensively  used.  The  State  owns  the  vitrified  brick 
manufacturing  establishments  and  employs  the  brick  only 


MATERIALS    OF    HIGHWAY   ENGINEERING  69 

on  State  Roads.     A  chemical  analysis  of  the  clay  at  one  of 
the  works  gave  the  following  results: 

Silica,  free 69.60  per  cent. 

Silica,  combined 10.51  " 

Alumina 8.70  " 

Ferric  Oxide 3.04  " 

Lime 0.85  " 

Carbonic  Acid 0.71  " 

Magnesia  Oxide 0.77  " 

Water 5.70 

Total ,   99.88  per  cent. 

Poor  quality  bricks  are  crushed  and  used  for  macadam 
construction. 

United  States.  WALTER  W.  CROSBY.  Bituminous 
binders  must,  first  of  all,  bind.  Their  power  to  adhere  to 
the  road  metal  must  be  of  the  highest.  Their  adhesive 
ability  must,  if  not  equal  to  their  cohesive  strength,  at 
least  be  sufficient  for  the  purposes  of  their  application  and 
vice  versa.  Consequently,  such  a  test  as  the  ductility  test, 
which  measures  the  ability  of  the  material  to  elongate 
without  rupture,  seems  insufficient  to  determine  the  true 
binding  ability  of  a  material,  and  a  better  test  should  be 
devised. 

Bituminous  materials  should  be  fluid  in  the  technical 
sense  of  the  term.  That  is,  they  must  impart  to  the  road 
surface  a  self-healing  ability  and  must,  as  far  as  practicable, 
be  so  far  from  being  brittle  as  to  successfully  resist  the 
shocks  of  ironshod  traffic  even  in  the  coldest  and  most 
hostile  weather.  Again,  when  successful  under  cold  weather 
conditions  as  regards  resistance  to  shocks,  they  must  not 


70  HIGHWAY   ENGINEERING 

become  so  fluid  under  warm  weather  conditions  as  to 
become  displaced  from  their  proper  position  in  the  road 
surface. 

They  should  be,  in  regard  to  these  characteristics,  as 
stable  as  possible  under  the  conditions  of  their  use.  If 
fluxed  to  meet  local  or  particular  conditions,  the  base  should 
still  be  of  a  character  which  will  preserve  the  above  charac- 
teristics, notwithstanding  the  temporary  presence  of 
the  flux. 

A  desirable  bituminous  binder  should  combine  the 
above  characteristics  with  the  least  practicable  admixture 
of  useless  or  possibly  obnoxious  adulterants. 

In  the  table  are  tabulated  tests  of  different  bituminous 
materials  used  by  the  writer  in  some  experimental  pieces 
of  road  built  under  his  direction  during  1909  and  1910. 

United  States.  PREVOST  HUBBARD.  When  making 
an  examination  of  bituminous  materials,  a  number  of 
factors  should  be  considered,  which  may  often  modify  to 
some  extent  the  method  to  be  employed.  Those  of  most 
importance  are  as  follows: 

1.  Purpose  for  which  the  material  is  to  be  used;    for 
instance,  as  a  dust  preventive  only,  as  a  semi-permanent 
binder  and  dust  preventive  for  surface  treatment,   or  as 
a  permanent  binder  in  construction  work. 

2.  Character  of  the  road  to  be  treated,  including  the 
type  of  road   (earth,   gravel,   or  broken  stone),   and   the 
physical  characteristics  of  the  road  material. 

3.  Desired  method  of  application;    namely,  whether 
the  material  is  to  be  applied  cold  or  hot,  by  means  of  a 
distributor    with    or  without    pressure,    by    pouring    from 
buckets,  or  as  a  prepared  mixture  with  the  road  material. 


TABLE  SHOWING  ANALYSIS  OF  BITUMINOUS  MATERIALS  USED  IN 


ANALYSIS 

] 

1 

(5) 

2 

(2) 

3 

(2) 

4 
(1) 

Water  soluble  Material  

None 
Trace  (1 
0.14%  (4) 

0.129% 
Trace  (4) 
0.20%  (1) 
7.17% 
0.9551 
349  Sec. 

None 
0.24% 

0.33% 
Trace  (1 
0.56%(1 
5.46% 
0.9788 
150  Sec. 

None 
2.96% 
4.525% 
8.12% 

5.51% 
1.075 
990  Sec. 
9  Sec. 

473  Sec. 
7% 
16 

62.5 

48°  C. 
14.75% 
17.5% 

6.5 

17.5 

72.  5°  C. 
21.75% 
27% 

2 
6.50 

87.  5°  C. 

0.49% 
69.95% 

Sticky 

None 
0.066% 

Free  Carbon,  insoluble  in  Carbon  Bi-Sulphide  . 
Insoluble  in  Carbon  Tetra-Chloride  

Ash  

0.05% 

25.55% 
1.202 
302  Sec. 

2 
14 

Fixed  Carbon  less  Free  Carbon  

Specific  Gravity 

Viscosity  at  100°  C.  Engler  .  .    . 

Lunge  Tar  tester  at  100°  C  

Lunge  Tar  tester  at  25°  C.  reading  to  1.4°..  .  . 
Loss  on  evaporation  at  105°  C.  21  hrs.  3}^"  dish 
Penetration  of  this  residue  at  4°  C 

(  Too  hard 
!    86  Sec. 
12.5% 

59.1 

I  Too  soft 
130 
39.  6°  C. 
14.1% 
16.6% 
Too  hard 
35 
Too  hard 
Too  soft 
116            I 
50°  C. 
25.25% 
28.2% 
Too  hard 
23 
Too  hard 
74.5 

69.  2°  C. 

0.94% 

77% 

Sticky 

81 

(1) 
(4) 

1  \ 

4) 
1) 
1) 

:s) 

:D 
;4) 
:D 
;4) 

36  Sec. 
1.85% 
Too  soft 

Too  soft 

Too  soft 
2.8% 
3.81% 
214         (1) 
Toosoft(l) 

Too  soft 

Too  soft 
4.22% 
6.35% 
146        (1) 
Too  soft 

Too  soft 

8°C.    (1) 
Too  soft 
0.42% 
93.9% 

Sticky 

358  Sec. 
9.5% 
Too  hard 

13 

58°  C. 
17.5% 

22% 

Too  hard 

Too  hard 

79°  C. 

26% 
29% 

Too  hard 
Too  hard 
87°  C. 

75 
1 

1 
2 

5 
1 
2 

a 
a 

8( 
2^ 
3( 

1 
1 

9: 

Penetration  of  this  residue  at  25°  C  « 

Melting  point  of  this  residue  

Loss  on  evaporation  at  170°  C.  2}^"  dish.  3  hrs. 
Loss  on  evaporation  at  170°  C.  2  3^"  dish.  5  hrs. 

Penetration  of  this  residue  at  4°  C  

i 
Penetration  of  this  residue  at  25°  C  < 

i 
Melting  point  of  this  residue  

Loss  on  evaporation  at  205°  C.  3  hrs  

Loss  on  evaporation  at  205°  C.  5  hrs  .... 

Penetration  of  this  residue  at  4°  C  .  . 

Penetration  of  this  residue  at  25°  C  

Melting  point  of  this  residue  

Paraffine  Scale  

Solubility  in  88°  Naphtha  

Character  of  residue  when  evaporated  on  glass 
Initial  temperature  of  Distillate  

214°  C. 
None 

None 

3% 

3% 
10% 

298°  C. 

211 

I 
C 

0 

] 

2 
14 

91 

Room  temperature  to  105°  C  

105°C.  to!70°C  

170°C.to225°C  

225°  C.  to  270°  C.. 

270°  C.  to300°C  

Temperature  when  Distillate  equals  the  %  loss 
on  evaporation  at  105°  C  

NOTE.    All  penetrations  given  are  with  No.  2  Standard  Needle,  100  gram  load. 
Key  to  names  of  materials:  1, 2, 3,  Asphaltic  compounds;  4, 4A,  7,  Refined  water-g 


39  ON  PARK  HEIGHTS  AVENUE,  BALTIMORE  COUNTY,   MARYLAND 


E  OF  MATERIAL 

A 

5 

6 

7 

8 

9 

REMARKS 

} 

(2) 

(1) 

(3) 

(1) 

(1) 

ne 

None 

None 

None 

None 

None 

7o 

28.17% 

24.19% 

1.20% 

0.19% 

28.59% 

0  23% 

ice 

0.16% 

9.33% 
1.25 
264  Sec. 

0.08% 

8.43% 
1.224 
169  Sec. 

0.05%  (1) 
Trace     (2) 
13.27% 
1.316 
20  Sec. 

V  .  .6/0  /Q 

Trace 

12.79% 
0.963 
2595  Sec. 

Trace 

6.39% 
1.235 
162  Sec. 

Analyses  are  carried  out  hi 
brm  and  according  to  method 
prescribed  by  the  Special  Com- 
mittee of  the  American  Society 
)f  Civil  Engineers  appointed  by 

c. 

0 

531  Sec. 
12.6% 

709  Sec. 
12.75% 

Too  fluid 
36.2% 

917  Sec. 
None 

373  Sec. 
9.75% 

igate  and  report  on  Bituminous 
Materials,  used  in  Road  Con- 
struction. 

ard 

Too  hard 

Too  hard 

Too  hard 

32 

3 

1 

20 

55°  C. 

17.48% 
21.6% 

13 

60°  C. 
13.90% 
17.10% 

25            (2) 
Too  hard  (1) 
53°  C. 
36.3% 
40.7% 

161 

42°  C. 

0.9% 
1.35% 

28 

48°  C. 
9.90% 
13.75% 

In  addition,  are  also  reported, 
'or  purposes  of  comparison  with 
other   records,    the    Losses    on 
Evaporation  at  105°  for  both  3 
and  5  hours  periods,  and  Pene- 

ard 

Too  hard 

Too  hard 

Too  hard  (2) 
30            (1) 

25 

Too  hard 

trations  and  Melting  points  of 
the  Residues;  the  losses  at  the 

ard 

15            (1) 
Too  hard  (1) 

67°  C. 
9.57% 

Too  hard 

73°  C. 

18% 

Too  hard  (2) 
120            (1) 

67.  8°  C. 
33% 

125 

50°  C. 

1.85% 

19.0 

50°  C. 
14.25% 

end  of  3  hours  under  Evapora- 
tion at  both  170°  and  205°;  the 
nitial  Temperatures  of  the  Dis- 
tillates;  and   the  Temperature 
when  the  amount  of  Distillate 

ard 

26.27% 
Too  hard 

22.10% 
Too  hard 

38.5% 
Too  hard   2) 
12             1) 

2.90% 
21 

19.25% 
Too  hard 

equals  the  Loss  on  Evaporation 
at  105°  for  5  hours. 

ard 

Too  hard  (1) 
8     (1) 

Too  hard 

Too  hard   2) 
65            (1) 

76 

2 

79°  C. 

76°  C. 

79°  C. 

66°  C. 

71°  C. 

38.8% 

38.8% 

1.49% 

Slightly 

80.80% 

Sticky 

Sticky 

163°  C. 

186°  C. 

129°  C. 

223°  C. 

130°  C. 

(3) 
(1) 

5%  water  (1) 
None     (1) 

None 

None 

None 

None 

e 

0.5%    (1) 
None     (1) 

None 

None     (1) 

None 

0.4% 

(y\ 

3.05%  (2) 

(Si 

1.5% 

1-4% 

13.9% 

0.1% 

1.3  % 

8.4% 

5.7% 

24.6% 

2% 

12.1% 

14.1% 

17.3% 

29.4% 

10.2% 

19.7% 

280°  C. 

290°  C. 

288°  C. 

296°  G. 

260°  C. 

figures  in  parentheses  (  )  indicate  number  of  samples  used  to  obtain  average. 
rs;  5,  6,  9,  Refined  coal  tars;  8,  Heavy  binding  oil. 


MATERIALS   OF   HIGHWAY   ENGINEERING  71 

In  the  latter  case,  it  is  also  desirable  to  know  whether  or 
not  the  road  material  itself  is  to  be  heated. 

4.  Quantity  and  character  of  traffic. 

5.  Climatic  conditions. 

Because  of  the  very  great  differences  between  oils  and 
tars,  somewhat  different  methods  of  examination  are 
followed.  A  summary  of  the  most  important  tests  for  each 
are  given  below: 

OIL   AND   OIL   PRODUCTS,    INCLUDING   FLUXED    ASPHALTS. 

1.  Specific  gravity. 

2.  Flash  point. 

3.  Melting  point  of  solids. 

4.  Penetration  of  semisolids  and  solids. 

5.  Volatilization  at  163  degrees  Centigrade  for  five  hours. 

6.  Solubility  in  carbon  bisulphide. 

(a)  Total  bitumen. 

(b)  Organic  matter  insoluble. 

(c)  Inorganic  matter. 

7.  Bitumen   insoluble   in  86  degree   Beaum6   paraffin 

naphtha. 

8.  Fixed  carbon. 

TAR   AND    OTHER  PRODUCTS. 

1.  Specific  Gravity. 

2.  Melting  point  of  solids. 

3.  Free  carbon. 

4.  Results  of  distillation. 

(a)  Water. 

(b)  Light  oils  to  110  degrees  Centigrade. 


72  HIGHWAY   ENGINEERING 

(c)  Second  light  oils  110  degrees  to  170  degrees 

Centigrade. 

(d)  Heavy  oils  170  degrees  to  270  degrees  Centi- 

grade. 

(e)  Pitch. 

The  values  of  the  various  tests  will  be  briefly  discussed. 

Specific  gravity: — Oil  with  a  specific  gravity  over  0.93 
must  be  heated.  No  oil  with  a  specific  gravity  under  0.95 
should  be  used  as  a  permanent  binder.  The  specific 
gravity  of  tar  is  largely  dependent  upon  the  percentage  of 
free  carbon.  As  a  rule  tars  with  specific  gravity  higher  than 
1.18  cannot  be  distilled  to  produce  satisfactory  road  binders 
unless  a  lighter  tar  is  mixed  with  them.  Tar  with  a  specific 
gravity  over  1.15  must  be  heated  before  using,  while  tars 
under  1.15  can  be  considered  merely  as  dust  layers  and 
temporary  binders. 

Flash  point: — The  flash  point  is  of  little  value  except 
as  a  quick  means  of  differentiating  between  heavy  crude 
oils  and  cut-back  products  or  fluid  residues.  Crude  oils 
usually'  have  a  lower  flash  point  than  residual  oils  and 
paraffin  oils  usually  flash  at  a  lower  point  than  asphaltic  oils. 

Melting  point : — The  determination  of  the  melting  point 
is  mainly  of  value  as  a  means  of  identification  and  for  control 
work  on  the  part  of  manufacturers,  -although  it  influences 
the  selection  of  material  to  conform  with  climate  to  some 
extent,  especially  in  the  case  of  tar  products.  If  the  pene- 
tration method  is  to  be  employed,  a  tar  product  should  have 
a  melting  point  not  over  25  degrees  Centigrade  and  a  blown 
oil  not  over  30  degrees. 

Penetration: — The  determination  of  penetration  is  of 
importance,  as  is  the  determination  of  the  melting  point, 


MATERIALS   OF   HIGHWAY   ENGINEERING  73 

for  work  of  identification  and  control.  The  test  also  in- 
fluences to  a  certain  extent  the  selection  of  materials.  For 
example,  no  oil  product  should  be  used  for  macadam 
construction  if  its  penetration  is  higher  than  25  millimeters 
at  25  degrees  Centigrade  with  a  number  2  needle,  unless  it 
possesses  the  property  of  hardening  when  subjected  to  the 
volatilization  test. 

Volatilization: — This  test  is  purely  arbitrary,  but  it 
is  of  considerable  value  when  applied  to  road  oils.  It 
consists  in  determining  the  loss  in  weight  of  20  grams  of 
oil  when  subjected  to  a  uniform  temperature  of  163  degrees 
Centigrade  for  five  hours  in  a  standard  size  dish.  If  a 
material  is  desired  to  maintain  a  certain  consistency  after 
application,  it  should  not  show  much  loss  by  volatilization; 
but  if  a  material  must  be  soft  at  time  of  application  because 
of  the  method  employed,  it  should  show  considerable  loss 
in  order  that  it  may  eventually  be  capable  of  attaining 
proper  consistency.  The  determination  of  penetration  of 
the  residue  is  important  as  showing  the  nature  of  the 
material  after  setting  up. 

Solubility  in  carbon  bisulphide: — The  test  is  especially 
important  for  tars  because  of  its  determination  of  the 
percentage  of  free  carbon.  A  knowledge  of  the  free  carbon 
content  is  very  important  both  for  determination  of  the 
class  of  the  tar  as  regards  manufacture  and  also  as  an  in- 
dication of  its  adaptability  for  various  forms  of  construction. 
The  effect  of  free  carbon  in  tars  from  the  standpoint  of  road 
treatment  has  been  investigated  by  the  author.  The  re- 
sults of  this  investigation  demonstrate  the  following  facts: 

1.  That  in  tars  of  the  same  consistency  those  of  low 
carbon  content  have  a  greater  inherent  binding  strength 
than  those  of  high  carbon  contents. 


74  HIGHWAY   ENGINEERING 

2.  That  in  tars  whose  bitumen  contents  are  of  the  same 
consistency,  those  of  high  carbon  contents  have  a  greater 
inherent  binding  strength  than  those  of  low  carbon  contents, 
but  that  the  binding  capacity  of  the  former  is  lower. 

3.  That  in  sand-tar  mixtures  containing  a  relatively 
large  amount  of  high  carbon  tar,  the  carbon  may  act  as  a 
filler,  and  add  to  the  mechanical  strength  of  the  mineral 
aggregate,  but  that  better  results  in  this  respect  can  be 
obtained  by  the  use  of  a  smaller  quantity  of  low  carbon 
tar  of  the  same  melting  point,  together  with  a  mineral 
filler. 

4.  That  the  waterproofing  value  of  high  carbon  tars  is 
in  general  less  than  that  of  low  carbon  tars. 

5.  That  free  carbon  retards  the  absorption  of  tars  by 
porous  surfaces. 

6.  That  when  tar  is  exposed  in  comparatively  thin 
films  free  carbon  has  little  or  no  effect  in  retarding  vola- 
tilization. 

In  view  of  the  foregoing  a  low  carbon  tar  is  preferable 
to  a  high  carbon  tar  for  surface  treatment  of  old  roads,  and 
also  in  construction  work,  provided  the  consistency  is  the 
same. 

Bitumen  insoluble  in  86  degree  Beaume  paraffin 
naphtha: — This  test  is  important  for  oils  as  indicating  the 
amount  of  body-forming  hydrocarbons  which  give  mechani- 
cal stability  to  the  materials.  No  oils  having  less  than  4 
per  cent  insoluble  will  be  valuable  except  as  dust  preventives. 
The  character  of  insoluble  matter  should  be  noted  as  to 
whether  or  not  it  is  sticky.  A  sticky  residue  indicates 
better  road  binding  qualities. 

Fixed  carbon: — This  test  is  an  indication  of  the  mechani- 
cal stability  of  an  oil.  Fixed  carbon  is  the  coke  resulting 


MATERIALS   OF    HIGHWAY   ENGINEERING  75 

from  the  ignition  of  the  material  away  from  the  air,  and 
should  not  be  confused  with  free  carbon.  It  is  not  a  very 
accurate  test,  and  hence  too  great  reliance  should  not  be 
placed  on^  it. 

Distillation: — As  applied  to  tars  it  is  very  valuable 
both  as  an  indication  of  their  road  binding  properties,  and 
the  method  of  preparation  if  they  are  refined  tars.  All  crude 
tars  contain  water,  and  the  amount  of  this  may  be  judged 
from  the  tests.  The  test  often  determines  whether  or  not 
the  product  is  a  mixture  of  tar  and  oil.  Refined  tars  should 
not  show  over  7  to  8  per  cent  by  volume  of  distillate  up 
to  170  degrees  Centigrade,  and  the  total  distillate  should 
show  when  cold  but  little  precipitated  naphthalene,  since 
this  substance  is  not  desirable  because  it  gives  a  false  con- 
sistency and  volatilizes  quite  readily. 


CHAPTER  VII 

FOUNDATION  AND  DRAINAGE 

BOLTZ,  JOHANN,  Imperial  Chief  Commissioner  of  Public 
Works,  Laibach,  Austria. 

LELI^VRE,  CHARLES,  Honorary  District  Inspector,  Ver- 
sailles, France. 

PIERCE,  VERNON  M.,  Chief  Engineer,  U.  S.  Office  of 
Public  Roads,  Washington,  D.  C.,  U.  S.  A. 

PIERRET,  LEOPOLD,  Chief  Engineer  of  Bridges  and  Roads, 
Amiens,  France. 

SKOUGAARD,  J.,  Director-General  of  Bridges  and  Roads, 
Christiania,  Norway. 

VANDONE,  ITALO,  Chief  Engineer  of  the  Province  of 
Milan,  Italy. 

VAN  VOLSOM,  EDGARD,  Engineer  of  Bridges  and  Roads, 
Brussels,  Belgium. 

Austria.  JOHANN  BOLTZ.  The  ordinary  foundation 
used  in  Austria  is  of  the  Telford  type.  Water  is  carried 
in  side  ditches,  and  the  old  custom  of  carrying  the  water 
across  the  road,  where  necessary,  in  surface  drains  is  giving 
way  of  late  in  favor  of  culverts. 

Belgium.  EDGARD  VAN  VOLSOM.  Stone  foundations 
are  the  most  commonly  used  for  macadam  roads.  Stones 
are  placed  by  hand  as  close  together  as  possible  and  wedged 
with  spawls.  The  stones  may  be  laid  on  the  bottom  of 

76 


FOUNDATION    AND    DRAINAGE  77 

the  road  trench  or,  where  conditions  demand,  upon  a  layer 
of  sand  or  cinders.  After  laying,  this  foundation  is  rolled 
with  a  steam  roller  to  a  uniform  thickness  of  6  inches,  7 
inches  or  8  inches  as  desired.  This  type  of  foundation  may 
be  strengthened  by  placing  stone  slabs  laid  flat  between  the 
ground  and  the  usual  form  of  foundation.  Concrete  and 
reinforced  concrete  have  not  as  yet  been  much  used  for 
foundations  for  macadam  roads. 

Paving  is  almost  always  laid  on  a  layer  of  sand  from  4 
inches  to  8  inches  thick,  spread  at  the  bottom  of  the  road 
trench,  unless  the  nature  of  the  ground  requires  the  in- 
troduction of  a  bed  of  cinders  between  the  ground  and  the 
sand  foundation.  As  a  rule  no  foundations,  properly 
so-called,  are  provided.  Nevertheless,  in  order  to  avoid 
the  sudden  deformations  which  occur  in  paving  laid  on  a 
sand  foundation  only,  unless  the  ground  is  particularly 
firm,  some  trials  of  paving  on  foundations  have  been  made 
in  Belgium.  The  City  of  Antwerp  has  used  foundations  of 
broken  stone  about  10  inches  thick  and  covered  with  2 
inches  of  sand.  This  form  has  proved  satisfactory.  In 
Brussels  broken  stone  and  refuse  destructor  slag  have  been 
used  together  for  foundations.  The  slag  contains  lime  and 
consequently  acts  as  a  binder  for  the  stone.  Satisfactory 
results  have  been  obtained  by  this  method.  Granulated 
slag  concrete  has  been  used  to  some  extent  placed  6  inches 
thick  and  covered  with  about  2  inches  of  sand.  In  one 
instance  the  cost  of  this  foundation  was  18  cents  per  square 
yard.  The  proportion  of  materials  used  for  this  concrete 
was  10  parts  slag  to  1  part  of  cement.  In  Brussels  a  founda- 
tion 6  inches  thick  of  broken  brick  mixed  with  a  mortar  of 
15  parts  sand  and  2J^  parts  of  hydraulic  lime  was  used. 
Concrete  slabs  were  used  at  Vilvorde.  The  slabs  were 


78  HIGHWAY   ENGINEERING 

made  of  7  parts  by  volume  of  granulated  slag  from  blast 
furnaces,  which  had  been  ground  and  mixed  with  1  part 
of  cement.  Two  sizes  of  slabs  were  used:  16  inches  by  17 
inches  by  6  inches  and  16  inches  by  16  inches  by  4  inches. 
A  sand  cushion  4  inches  in  depth  was  placed  between  the 
blocks  and  the  slabs.  Good  results  were  not  obtained  be- 
cause the  blocks  were  tapered  too  much  and  the  sand  layer 
was  too  thick. 

France.  CHARLES  LELIEVRE.  Sand  foundations  are 
valuable  under  both  pavements  and  macadam  roads.  The 
incompressibility  of  such  a  foundation,  as  well  as  its  cushion 
effect  to  prevent  abrasion  of  the  two  adjacent  courses,  recom- 
mends it  for  use  under  pavements.  The  use  of  sand  under  mac- 
adam roads  is  a  later  development,  but  is  found  very  bene- 
ficial where  the  ground  is  loose  but  not  waterlogged  and  for  the 
general  prevention  of  the  substratum  oozing  through  the  stone 
layers.  Sand  foundations  should  be  wet  and  well  rammed. 

Brick  and  plaster  rubbish  compressed  to  a  thickness 
of  from  4  inches  to  8  inches  is  often  very  efficacious. 

Simple  lime  concrete  and  ordinary  cement  concrete  of 
various  proportions  is  laid  4J/2  inches  to  8  inches  thick  for  a 
foundation. 

Reinforced  concrete  is  used  in  order  to  give  more 
rigidity  to  the  foundation.  The  transversal  reinforcement 
bars  tie  the  longitudinal  ones  together,  their  number  varying 
according  to  the  intensity  of  traffic. 

Paving  on  an  old  macadam  surface  is  practical  and 
advantageous.  The  old  road  must,  however,  be  reprofiled, 
drained  and  covered  with  a  thin  bed  of  sand. 

Given  an  equal  thickness,  it  is  possible  to  classify  in 
order  of  increasing  resistance  the  different  kinds  of  founda- 
tions as  follows: 


FOUNDATION   AND    DRAINAGE  79 

1.  Quarried  stone  or  pieces  of  stone  of  all  sizes  simply 
spread  on  the  bed. 

2.  Stone  or  flags  placed  flat  to  form  a   distributing 
footing. 

3.  Pointed  stone  with  the  joints  wedged  by  hand  and 
with  small  stone  and  sand  filling. 

4.  Rough-hewn  stone  on  edge  bonded  in  form  of  an 
arch. 

5.  A  homogeneous  mass  of  coarse  shingle,  3  inches  to  4 
inches  in  size,  well  compressed. 

6.  A  mass  of  coarse  shingle  or  gravel,  1J4  inches  to  2^ 
inches,  well  rolled. 

7.  A  mass  of  clean  sand,  compacted  and  compressed. 

8.  The  same  mass  watered  with  milk  of  lime. 

9.  Masonry. 

10.  Concrete  with  hydraulic  mortar. 

11.  Concrete  in  cement  mortar. 

12.  Reinforced  concrete. 

The  information  which  has  been  supplied  from  the 
different  Departments  of  Roads  of  France  shows  that 
the  most  widely  used  form  of  foundation  on  roads  located 
outside  the  towns  and  villages,  particularly  on  the  old  main 
roads,  is  stone  blocks  varying  from  6  inches  to  8  inches  or 
even  10  inches  thick,  placed  in  position  by  hand,  system 
Tresaguet,  or  a  bed  of  coarse  shingle  or  flags  of  sandstone 
from  3^£  inches  to  4  inches  by  6  inches  to  8  inches  thick. 
In  modern  roads  there  has  been  employed  a  layer  of  packed 
stone  of  6  inches  to  8  inches  thick  resting  directly  on  the 
substratum  or  on  a  bed  of  gravel,  sand  or  plaster  and  brick 
rubbish.  Also,  a  simple  bed  of  sand  6  inches  to  10  inches 
thick  under  the  stone  metalling  has  been  used  in  certain 


80  HIGHWAY   ENGINEERING 

cases  and  occasionally  a  bed  of  concrete  5  inches  to  6  inches 
thick. 

It  is  of  the  utmost  importance  to  secure  thorough 
drainage.  To  secure  surface  drainage  removal  of  mud  is 
a  necessity.  After  the  road  is  cleaned  and  is  soft  from  being 
impregnated  with  moisture,  as  is  the  case  after  a  thaw,  the 
use  of  a  heavy  roller  is  advantageous.  Protective  coatings 
of  bituminous  substances  on  the  surfaces  of  roadways  as  a 
rule  aid  surface  drainage.  Roadsides  should  be  sloped  well 
and  should  preferably  be  compacted  with  sand  or  rough  stone. 

kaised  shoulders  at  one  time  existed  along  the  greater 
portion  of  the  main  roads;  but  recently,  unless  the  grades 
are  steep  and  paved  gutters  and  curbs  are  employed,  the 
simple  roadside  is  preferred.  The  value  of  the  raised  shoul- 
der on  steep  grades  lies  in  the  prevention  of  the  cutting  of 
the  roadside  by  vehicles,  which  in  descending  use  the 
shoulder  as  a  brake  because  of  its  greater  resistance  to 
traction.  The  chief  disadvantages  of  the  raised  shoulder 
are:  first,  that  in  level  regions  the  flow  of  surface  water 
from  the  road  is  hindered  and,  second,  that  the  cross  gutters 
which  are  necessitated  for  allowing  the  water  to  run  off  are 
disagreeable  for  foot  passengers  unless  they  are  bridged  over 
at  considerable  expense. 

Side  ditches  aid  in  the  drainage  of  a  road  and  prevent 
infraction  of  rights  of  adjacent  landowners.  Riparian 
owners  should  be  compelled  to  build  crossovers  over  ditches 
at  their  own  expense.  Percolation  pits  are  sometimes 
used  for  securing  underground  drainage.  This  form  of 
drainage  consists  simply  in  digging  through  an  impervious 
layer  to  a  pervious  layer  and  filling  the  hole  with  rough 
stone.  It  is  applicable  only  in  cases  where  the  impervious 
layer  is  thin. 


FOUNDATION   AND   DRAINAGE  81 

The  depth  at  which  drains  should  be  laid  beneath  the 
road  surfaces  should  not  be  lower  than  2  feet,  3  inches,  to 
2  feet,  6  inches,  and  the  spacing  of  the  lines  of  drain  may 
vary  from  16  feet  to  50  feet.  There  should  always  be,  how- 
ever, a  relation  between  the  depth  and  the  spacing  accord- 
ing to  the  retentive  power  of  the  ground  for  water.  The 
gradients  of  the  drains  should  not  be  less  than  0.002  for  pipes, 
and  0.005  for  stone  conduits.  The  maximum  slope  should 
not  exceed  0.03  or  0.035  per  thousand.  The  most  common 
form  of  underground  drain  is  loose  stone  or  flagging  shaped 
in  the  form  of  a  conduit.  Earthenware  pipes  are  seldom  used 
because  of  liability  of  breaking. 

France.  LEOPOLD  PIERRET.  Metalled  roads  should 
be  laid  on  foundations  on  all  ground  other  than  frost  proof 
rock.  Rock  which  is  not  frost  proof  should  be  excavated 
below  the  frost  line  and  the  excavation  filled  with  good  earth 
or  sand.  In  sandy  clay,  sand  or  clay  excavations,  the 
foundation  may  consist  of  a  layer  of  a  poorer  and  a  larger 
grade  of  stone  than  is  used  in  the  wearing  surface.  The 
thickness  of  the  foundation  varies  between  4  inches  and  9 
inches,  depending  upon  the  quality  of  the  metal  selected, 
the  nature  of  the  soil,  the  amount  and  nature  of  the  traffic. 
In  constructing  metalled  roads  in  marshy  or  soft  lands 
special  methods  have  to  be  adopted,  such  as  layers  of  fascines 
or  of  brushwood.  Drainage  should  be  provided  in  all  cases. 

Paved  roads  must  always  be  laid  on  foundations  of 
sand  varying  in  thickness  from  2  inches  to  10  inches.  The 
foundation  is  placed  directly  on  the  surface  of  the  ground 
if  it  is  frost  proof  or  if  well  drained.  In  cases  where  the 
ground  cannot  be  well  drained,  the  earth  should  be  taken 
out  to  a  depth  of  8  inches  to  9  inches  and  replaced  with 
sand.  The  sand  used  must  be  clean  and  of  medium  size.  It 


82  HIGHWAY   ENGINEERING 

should  be  spread  in  layers  3  inches  to  4  inches  in  thickness 
which  should  be  carefully  watered  and  rammed. 

In  towns  the  importance  of  the  traffic  may  justify 
the  construction  of  a  concrete  foundation  from  4J^  inches 
to  8  inches  in  thickness.  A  layer  of  sand  2  inches  to  4 
inches  thick  should  be  placed  between  the  pavement  and 
the  foundation  to  act  as  a  cushion. 

Italy.  ITALO  VANDONE.  In  the  construction  of  a 
road  from  Binasco  to  Rosate  in  the  Province  of  Milan, 
the  subsoil  encountered  was  a  fine  gravel  covered  with  a 
thin  coat  of  mould.  The  section  built  had  a  concrete 
foundation  under  the  centre  of  the  road,  the  theory  being 
that  the  travel  would  largely  be  concentrated  at  the  centre. 
This  foundation  had  a  width  of  approximately  9  feet,  and 
depths  of  5J/2  inches  at  the  centre  and  4%  inches  at  the 
sides.  The  crown  of  the  road  was  given  an  elliptical  form. 

Norway.  J.  SKOUGAARD.  Particular  care  is  taken 
in  the  building  of  State  Roads  in  Norway  that  a  very  thor- 
ough drainage  of  the  subsoil  is  secured. 

Underground  drainage  is  usually  secured  by  ditches 
at  each  side  of  the  road,  or  frequently,  where  the  ground 
slope  is  at  right  angles  to  the  direction  of  the  road,  one 
ditch  on  the  upper  side  is  sufficient.  These  ditches  are  dug 
to  a  depth  of  from  18  inches  to  24  inches  with  side  slopes 
of  1  to  1.5,  the  width  at  the  top  varying  from  3  feet  to  5 
feet.  In  marshy  ground  the  ditches  are  dug  to  a  depth  of 
about  3  feet  and  a  space  from  3  feet  to  5  feet  is  left  between 
the  road  and  the  edge  of  the  ditch.  When  the  road  is  cut 
into  rock,  the  ditches  are  cut  about  18  inches  deep  with  a 
bottom  width  of  14  inches  to  18  inches. 

It  is  customary  to  construct  at  intervals,  not  usually 
exceeding  325  feet,  small  bridged  conduits  across  the  road. 


FOUNDATION   AND   DRAINAGE  83 

These  conduits  are  used  in  large  embankments  where 
the  roads  encounter  an  infiltration  of  water,  and  are  built 
with  good  gradients  towards  the  ditches.  They  are  usually 
constructed  as  covered  drains  of  dry  stone  masonry  with  a 
cross-section  of  about  2  feet  by  2  feet,  but  the  dimensions 
vary  under  different  conditions.  Reinforced  concrete  pipes 
are  often  employed  in  place  of  dry  masonry  construction. 
In  ground  consisting  of  unstable  sandy  clay  a  system  of 
drainage  consisting  of  closed  drains  laid  in  the  roadbed  is 
frequently  employed.  These  drains  are  filled  with  stones. 
In  clay  or  marshy  ground  a  bed  of  sand  is  frequently  laid 
below  the  foundations. 

United  States.  VERNON  M.  PIERCE.  The  improved 
roads  of  the  United  States  may  be  divided  into  four  classes, 
according  to  the  method  in  which  the  foundation  is  formed : 
(1)  those  having  no  artificial  foundation,  but  in  which  the 
covering  materials  are  placed  directly  on  the  natural  soil, 
the  surface  of  the  ground  being  shaped  only;  (2)  roads 
having  a  paved  foundation;  (3)  roads  having  a  foun- 
dation of  concrete;  (4)  those  having  miscellaneous 
foundations  of  material  such  as  gravel,  broken  field  stone, 
cinders,  brickbats,  etc.  Of  the  approximately  200,000 
miles  of  improved  road  in  the  United  States,  by  far  the 
largest  mileage  comes  under  the  first  class.  This  is  per- 
fectly natural.  The  demand  is  constantly  for  a  road  at 
the  lowest  possible  cost.  This  has  led  not  only  to  a  con- 
siderable reduction  in  the  thickness  of  our  macadam  roads, 
but  also  to  a  utilization  of  the  natural  soil  as  a  foundation 
wherever  possible.  Many  failures  have  resulted,  but  the 
failures  have  not  been  without  their  value,  for  from  these 
failures  as  well  as  the  successes  certain  fundamental  facts  and 
principles  have  been  impressed  so  strongly  on  the  road 


84  HIGHWAY   ENGINEERING 

builders  that  fewer  mistakes  and  failures  are  likely  to  result 
in  the  future. 

The  United  States  presents  a  great  variety  of  conditions 
in  climate,  topography,  soils,  and  character  of  traffic. 
Naturally,  the  construction  will  have  to  be  modified  to  meet 
the  various  requirements,  and  this  fact  must  be  borne  in 
mind,  for  while  the  most  general  practice  is  here  set  down, 
there  are  frequent  and  marked  deviations  arising  from  our 
varied  local  conditions. 

Earth  foundations  should  be  carefully  drained,  thorough- 
ly compacted,  crowned  the  same  as  the  finished  road,  and 
should  be  freed  from  all  vegetable  matter.  Where  the  road 
is  built  on  an  embankment,  the  earth  fill  should  be  laid 
in  layers  not  exceeding  6  inches  in  depth  and  each  layer 
thoroughly  compacted  with  a  roller.  If  necessary,  water 
should  be  added  so  that  the  material  will  puddle  well. 

Paved  foundations  are  usually  known  as  telford 
foundations  in  the  United  States.  They  are  much  less 
frequently  used  than  earth  foundations.  The  common 
method  employed  is  to  use  stones  about  6  inches  to  8  inches 
high,  3  inches  to  8  inches  wide,  and  6  inches  to  15  inches 
long  placed  with  their  longest  dimensions  at  right  angles 
to  the  axis  of  the  road.  Spawls  are  used  to  wedge  the 
stones.  The  foundation  is  rolled  with  a  power  roller,  and 
stones  which  show  a  tendency  to  shift  position  materially 
should  be  removed.  This  method  is  expensive  in  the  United 
States  because  of  the  high  cost  of  hand  labor  and  teams. 

Concrete  foundations  are  probably  the  best  road 
foundations  in  use  at  the  present  time.  Concrete  is  strong 
and  practically  homogeneous  and  therefore  able  to  dis- 
tribute the  stresses  from  traffic  over  a  considerable  area, 
and  is  in  addition  fairly  impervious,  so  that  it  assists  in 


FOUNDATION   AND    DRAINAGE  85 

protecting  the  soil  subgrade  from  surface  moisture.  Both 
Portland  and  natural  cements  are  used,  but  the  use  of 
Portland  is  much  the  greater.  Concrete  is  used  very  largely 
for  the  foundations  of  city  pavements,  and  is  being  used 
somewhat  in  country  districts  as  a  foundation  for  brick  or 
bituminous  macadam  surfaces.  The  general  tendency  is 
to  lessen  the  thickness  of  concrete  foundations,  the  former 
practice  being  to  build  them  8  inches  in  depth,  while 
6  inch  and  even  4  inch  concrete  foundations  are  now 
common.  The  concrete  should  be  laid  in  strips  across  the 
full  width  of  the  road  as  soon  as  possible  after  mixing  and 
then  tamped  or  rolled  with  a  light  roller. 

Among  the  miscellaneous  foundations  used  are  those 
built  of  broken  stone,  brickbats,  gravel,  materials  scarified 
from  old  pavements  or  roads,  logs,  planks,  and  slag.  The 
first  four  forms  are  built  from  4  inches  to  12  inches  in 
thickness  and  should,  as  a  rule,  be  filled  with  sand.  Logs 
are  sometimes  used  in  land  where  the  level  of  the  ground 
water  is  practically  always  at  the  surface  of  the  ground. 
Such  construction  is  called  a  corduroy  road.  Plank  founda- 
tions are  cheaper  and  more  satisfactory,  and  hence  are  more 
frequently  used.  Slag  from  iron  and  steel  furnaces  and 
ore  smelters  has  been  successfully  used.  Acid  slag  forms 
only  a  physical  bond,  while  basic  slags  form  a  chemical 
bond  which  binds  all  the  particles  together  thus  forming  a 
homogeneous  foundation.  It  seems  probable  that  slag 
foundations  will  be  a  success  and  prove  economical  in  some 
localities  after  further  experimental  work. 

The  most  important  principle  involved  in  road  build- 
ing is  that  of  thorough  and  proper  drainage.  The  soil 
upon  which  the  road  bed  is  placed  must  eventually  bear 
the  loads  passing  over  the  road.  The  intensity  of  the 


86  HIGHWAY   ENGINEERING 

pressure  is  of  course  not  nearly  so  great  on  the  soil  as  on 
the  wearing  surface  of  the  road,  since  the  severe  wheel 
pressure  becomes  distributed  over  a  much  larger  area,  the 
amount  of  distribution  depending  on  the  thickness,  character 
and  condition  of  the  roadway  materials.  But,  whatever 
the  distribution,  the  load  is  finally  transmitted  to  the  soil. 
Most  soils  can  be  so  compacted  as  to  form  a  good  firm  foun- 
dation as  long  as  they  are  kept  dry. 

Surface  drainage  is  accomplished  by  using  more  or 
less  impervious  materials  for  the  surface  coat  and  by 
having  the  crown  of  the  road  sufficient  to  throw  the  water 
off. 

Ditches  and  cross  drains  should  be  designed  to  take 
the  largest  storm  flow.  The  grade  of  the  bottom  of  a 
ditch  should  not  be  less  than  6  inches  in  100  feet.  As  a 
rule  gutters  or  side  ditches  in  the  country  are  unpaved  ex- 
cept on  steep  grades. 

Cross  drains  or  culverts  are  made  of  wood,  earthen- 
ware, iron,  cement  and  concrete,  both  reinforced  and 
plain.  Iron  and  reinforced  concrete  seem  to  be  the  materials 
best  adapted  to  a  cold  climate  because  of  the  liability  of 
other  forms  to  crack  by  clogging  and  subsequent  freezing. 
All  culverts  should  have  their  ends  protected  by  concrete 
headwalls. 

Tile  pipe  is  generally  used  for  removal  of  ground  water. 
A  line  of  tile  pipe  may  be  placed  on  both  sides,  on  one  side 
only,  or  under  the  center  only,  according  to  the  conditions 
met  with.  Where  the  flow  of  ground  water  is  mostly  in 
one  direction,  one  line  of  tile  pipe  on  the  side  to  keep  it 
away  from  the  road  is  sufficient.  In  heavy  soils  two  lines 
of  pipe  will  often  be  found  necessary.  In  these  soils  it  is 
well  to  lay  the  tile  pipe  on  a  layer  of  sand  about  4  inches 


FOUNDATION    AND    DRAINAGE  87 

deep  and  cover  it  with  sand  to  a  depth  of  at  least  1  foot. 
This  plan  prevents  the  pores  of  the  pipe  from  becoming 
clogged. 

One  of  the  later  methods  employed  to  drain  the  sub- 
soil which  has  given  satisfaction,  is  the  construction  of  the 
"V"  drain.  In  this  work  the  subgrade  should  be  excavated 
for  the  full  width  of  the  surfaced  roadway,  from  6  inches  to  8 
inches  deeper  at  the  sides,  and  from  12  inches  to  18  inches 
deeper  at  the  center  than  usual,  thus  producing  a  flattened 
"V"  shaped  trench.  This  extra  excavation  is  filled  with 
pebbles  and  boulders  varying  in  size  from  J/2  inch  to 
12  inches  in  their  longest  dimensions.  The  largest  stones 
are  placed  in  the  bottom  of  the  trench,  which  should  be 
graded  longitudinally  so  that  the  water  will  run  easily. 

Details  of  the  practice  of  sub-drainage  vary  largely  in 
the  different  sections  but  the  employment  of  longitudinally 
tiled  and  "V"  shaped  drains  to  collect  and  carry  off  the 
water  is  very  extensive  and  is  rapidly  increasing.  Road 
builders  are  learning  more  and  more  from  experience  that 
as  a  rule  it  is  cheaper  in  the  end  and  more  satisfactory  to 
drain  the  roads  than  to  lay  expensive  foundations.  To  keep 
the  earth  dry,  hard,  and  unyielding  is  necessary  to  secure 
low  cost  of  maintenance  and  long  life  of  a  road.  Therefore, 
the  water  falling  on  the  road  must  be  carried  off  quickly 
and  effectively  and  the  water  from  below  must  be  inter- 
cepted and  removed  before  it  reaches  the  road  bed  where  it 
can  do  damage. 


CHAPTER  VIII 

MACADAM  AND  GRAVEL  ROADS 

DE  JAEGERE,  ALBERIC,  Civil  Engineer,  Antwerp, 
Belgium. 

FLETCHER,  AUSTIN  B.,  M.  Am.  Soc.  C.  E.,  Secretary, 
Massachusetts  Highway  Commission,  Boston,  Mass.,  U.  S.  A. 

GLASNER,  ANTOINE,  Engineer,  Budapest,  Hungary. 

KARAKOULAKOFF,  PAUL,  Engineer,  Ministry  of  Public 
Works,  Sofia,  Bulgaria. 

LE  GAVRIAN,  P.,  Engineer  of  Bridges  and  Roads,  Ver- 
sailles, France. 

MIKHAILOFF,  PAUL,  Engineer  of  Highways,  St.  Peters- 
burg, Russia. 

RABLIN,  JOHN  R.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer, 
Metropolitan  Park  Commission,  Boston,  Mass.,  U.  S.  A. 

SKOUGAARD,  J.,  Director-General  of  Bridges  and  Roads, 
Christiania,  Norway. 

Belgium.  ALBERIC  DE  JAEGERE.  The  first  class 
macadam  roads  of  Belgium  consist  of  a  layer  of  rough-hewn 
stone  and  spalls  7  inches  in  thickness  covered  by  two 
layers  of  broken  stone  which  together  make  a  thickness  of 
5  inches  after  compacting. 

The  bed  of  the  foundation,  previously  dressed  parallel 
to  the  finished  surface,  is  rolled  by  means  of  horse  drawn 
rollers  weighing  6  tons  with  their  ballast  load.  The  rough 
stones  are  set  so  that  their  greatest  dimensions  are  at  right 
angles  to  the  road  axis  and  are  wedged  together  by  a  maul 


MACADAM  AND  GRAVEL  ROADS  89 

in  such  a  manner  that  after  this  operation  it  is  not  possible 
to  remove  a  single  piece  without  using  considerable  force. 
This  course  is  compacted  to  the  prescribed  thickness  of  7 
inches.  On  this  stone  bedding,  previously  cleared  of  all 
debris,  is  spread  the  first  bed  of  metalling,  which  is  com- 
pacted until  no  further  impression  can  be  made  on  it.  The 
roadway  is  afterwards  covered  with  the  second  layer  of 
metal  to  the  required  thickness,  which,  after  rolling,  forms 
the  desired  profile.  The  rolling  of  the  second  layer  of 
metal  is  continued  in  such  a  manner  as  to  compact  the 
whole  mass  thoroughly  and  to  form  a  uniform  surface,  the 
metalling  of  which  does  not  spring  under  the  roller.  The 
requisite  quantity  of  fine  material  is  spread  gradually  and  as 
uniformly  as  possible  during  the  continued  rolling,  and  is 
forced  into  the  metalling  by  means  of  wire  brooms.  The 
rolling  is  performed  by  means  of  a  steam  roller  weighing  at 
least  14  tons,  and  is  accompanied  by  watering,  using  7 
gallons  per  square  yard  of  surface.  Constructed  under 
such  conditions,  the  macadam  costs  about  81  cents  per 
square  yard.  The  repairing  of  this  surface  is  done  by  means 
of  remetalling;  namely,  by  spreading  a  new  bed  of  fine 
metal  and  rolling  with  a  steam  roller.  The  life  of  macadam, 
with  the  exception  of  the  remetalling,  is  nearly  infinite, 
because  the  hewn  stone  which  forms  the  foundation  is 
never  subjected  to  wear.  The  cost  of  maintenance  per 
square  yard  per  annum  is  on  an  average  from  6.5  cents  to 
8  cents.  This  is,  therefore,  a  very  economical  road  surface, 
but  it  is  not  suitable  for  streets  which  have  heavy  traffic. 
In  towns,  macadam  is  now  only  used  for  park  roads  and  on 
certain  parts  of  boulevards. 

Bulgaria.     PAUL  KARAKOULAKOFF.     In  the  construc- 
tion of  macadam  roads  in  Bulgaria  the  surface  stratum  is 


90  HIGHWAY   ENGINEERING 

laid  on  a  bottom  course  of  quarry  stone  6  inches  to  8  inches 
in  thickness,  the  stones  being  of  a  truncated  pyramid  section. 
This  bottom  course  is  always  laid  on  a  foundation  well 
levelled  and  rolled.  On  firm  ground  it  is,  from  motives 
of  economy,  made  of  rubble  instead  of  quarry  stones.  On 
the  bottom  course  a  layer  of  metalling  or  gravel  about  6 
inches  to  8  inches  in  thickness  is  laid.  The  size  of  broken 
stone  varies  from  1J/2  inches  to  2/3  inches  according  to  the 
quality  of  the  stone.  When  the  metal  surfacing  has  no 
foundation  below  it,  its  thickness  varies  between  8  inches 
and  14  inches  according  to  the  degree  of  firmness  of  the 
ground.  Finally,  after  the  metal  surfacing  has  been  thor- 
oughly compacted,  a  layer  of  sand  or  stone  chips  from  %  of  an 
inch  to  1J/2  inches  in  thickness  is  spread  over  it  and  rolled. 

France.  P.  LE  GAVRIAN.  Among  the  limestone  bind- 
ers which  may  be  used  in  macadam  road  construction  are 
included  calcareous  sand,  marl,  chalk  and  soft  limestones, 
dolomite,  etc.,  all  of  them  being  substances  which,  if  mixed 
with  stone  of  a  hard  nature,  such  as  flint,  quartz,  etc.,  form 
a  magma  of  material  easily  consolidated  but  without  any 
real  setting.  These  materials  make  up  for  the  want  of 
cohesion  of  hard,  smooth  substances,  which  compression 
alone  could  never  solidly  bind  together.  A  number  of  these 
materials  have  been  used  for  a  long  time  past  in  a  great 
many  parts  of  France  where,  indeed,  they  are  still  regularly 
and  ordinarily  employed  for  road  metalling.  These  per- 
ceptible inert  binding  mixtures,  while  being  good  enough 
for  highways  bearing  a  moderate  amount  of  traffic,  are 
quite  insufficient  on  roads  with  much  traffic  on  them, 
especially  if  it  consists  of  highspeed  automobiles. 

Hungary.  ANTOINE  GLASNER.  In  the  construction 
of  the  usual  type  of  metalled  roads  a  layer  of  metal  4  inches 


MACADAM  AND  GRAVEL  ROADS  91 

to  4y/3  inches  deep  is  rolled  with  a  steam  roller  until  the 
pieces  of  stone  are  levelled  to  the  desired  profile  and  form 
a  layer  firm  enough  to  preserve  its  cohesion  under  a  light 
vehicle.  The  rolling  is  accomplished  by  means  of  a  steam 
roller  weighing  from  13  to  15  tons,  water  being  sprinkled  on 
the  surface  as  the  rolling  progresses.  Then  a  layer  of  chips 
%  of  an  inch  deep  is  laid  over  the  surface  and  rolled.  The 
chips  are  forced  into  the  interstices  of  the  surface  by  the 
pressure  of  the  roller,  thus  forming  a  firm  mosaic  like 
structure.  Even  in  this  condition,  however,  the  road  is 
not  opened  to  traffic  until  a  covering  of  sand  from  ^  of  an 
inch  to  24  of  an  inch  deep  is  spread  over  it. 

Norway.  J.  SKOUGAARD.  The  great  majority  of  our 
roads  are  constructed  with  a  broken  stone  surface  resting 
on  a  layer  of  rough-hewn  stone.  It  is  a  method  of  con- 
struction which,  with  some  slight  modifications,  has  been 
maintained  by  us  since  the  introduction  of  modern  systems 
of  road  design  in  Norway. 

For  some  years  past  rolling  has  been  more  and  more 
common,  a  horse  drawn  roller  being  employed.  The  use 
of  binding  material  is  always  necessary,  clayey  gravels 
being  preferably  used  or,  if  such  material  is  not  procurable, 
clay  itself.  The  fine  binding  materials  are  usually  spread  on 
the  road,  after  the  stone  surface  is  thoroughly  rolled,  in 
such  quantity  as  to  fill  the  interstices  and  slightly  cover  the 
metal  itself.  Then  follows  a  careful  rolling,  after  which  the 
roadway  is  again  covered  with  a  thin  layer  of  clean  gravel. 

Russia.  PAUL  MIKHAILOFF.  In  Russia  the  macadam 
type  of  road  is  usually  adopted,  the  thickness  of  metalling 
varying  from  6  inches  to  10  inches  laid  on  a  foundation  of 
sand  and  gravel.  When  clay,  marl  or  peaty  soil  is  en- 
countered, it  is  customary  to  excavate  and  spread  a  6  inch 


92  HIGHWAY  ENGINEERING 

layer  of  sand  to  secure  drainage  and  the  stability  of  the 
thin  stone  metalling.  By  such  a  method,  the  water  is  kept 
from  penetrating  the  stone  layer  and  good  results  have 
ensued. 

United  States.  AUSTIN  B.  FLETCHER.  The  method 
of  construction  of  macadam  roads  in  Massachusetts  is  as 
follows:  After  properly  shaping  and  rolling  the  subgrade, 
broken  stone  is  laid  so  that  the  depth  after  rolling  will  be 
6  inches  at  the  center  and  4  inches  at  the  sides.  This  depth 
is  varied  according  to  traffic  and  subsoil  conditions.  The 
bottom  course  consists  of  stones  varying  from  1%  inches  to 
2f/2  inches  in  their  longest  dimensions,  and  the  upper  course 
of  stones  varying  from  J/£  inch  to  1 J4  inches  in  their  longest 
dimensions,  the  depth  of  the  courses  being  usually  4  inches 
for  the  lower  and  2  inches  for  the  upper.  Each  course  is 
rolled  with  a  roller  weighing  from  10  to  15  tons.  After  both 
courses  are  thoroughly  compacted,  broken  stone  screenings, 
containing  the  fine  dust,  are  spread,  watered  and  rolled  until 
the  interstices  of  the  stone  are  substantially  filled. 

A  15  foot  road  of  this  type  will  require  about  1  ton  of 
trap  rock  per  3.13  square  yards.  These  roads  have  given 
excellent  results  until  the  advent  of  the  motor  car. 

United  States.  JOHN  R.  RABLIN.  In  the  early  de- 
velopment of  the  Metropolitan  Park  System  of  Boston  it 
was  found  that  macadam  roadways  built  with  a  soft  grade 
of  stone  were  much  more  easily  maintained  than  those 
constructed  with  trap  rock.  The  class  of  traffic  on  these 
roads  does  not  wear  trap  or  other  hard  rock  enough  to 
supply  the  binder  necessary  to  keep  the  roads  in  good 
condition.  The  stripping  of  the  surface  of  ordinary  mac- 
adam roads  by  the  motor  vehicle  traffic  has  made  it  neces- 
sary to  adopt  other  methods  of  construction. 


CHAPTER  IX 

DUST  PREVENTION  BY  THE   USE  OF  PALLIATIVES 

BALLO,  ALFRED,  Commissioner  of  Street  Cleaning, 
Budapest,  Hungary. 

FRANZE,  GUSTAV,  Commissioner  of  Public  Works, 
Frankfort-on-the-Main,  Germany. 

FROIDURE,  EUGENE,  Principal  Engineer  of  Bridges  and 
Roads,  Ypres,  Belgium. 

KARAKOULAKOFF,  PAUL,  Engineer,  Ministry  of  Public 
Works,  Sofia,  Bulgaria. 

LE  GAVRIAN,  P.,  Engineer  of  Bridges  and  Roads,  Ver- 
sailles, France. 

RABLIN,  JOHN  R.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer, 
Metropolitan  Park  Commission,  Boston,  Massachusetts, 
U.  S.  A. 

SKOUGAARD,  J.,  Director  General  of  Bridges  and  Roads, 
Christiania,  Norway. 

SPERBER,  Chief  Engineer,  Hamburg,  Germany. 

VERSTRAETE,  RICHARD,  Engineer  of  Bridges  and  Roads, 
Bruges,  Belgium. 

Belgium.  EUGENE  FROIDURE  and  RICHARD  VER- 
STRAETE. The  use  of  calcium  chloride  will  not  supplant 
surface  tarring  in  Belgium.  The  process  is  temporary  in 
effect  and  is  rendered  useless  if  a  rain  occurs  soon  after 
application. 

Bulgaria.    PAUL   KARAKOULAKOFF.    In   the   combat- 

93 


94  HIGHWAY    ENGINEERING 

ing  of  dust,  Bulgaria  has  not  as  yet  achieved  anything  of 
consequence.  No  coal  tar  is  produced  in  the  Kingdom, 
and  wood  tar  is  produced  only  in  inconsiderable  quantities. 
Hence,  the  tarring  system  is  too  costly  to  install.  The 
efforts  of  road  engineers  are  largely  directed  toward  improve- 
ment of  present  conditions  by  the  use  of  materials  which 
will  not  crumble  easily. 

France.  P.  LE  GAVRIAN.  The  use  of  oils  as  pallia- 
tives is  very  limited  in  France.  There  are,  however,  many 
emulsions  in  use,  a  typical  one  being  Westrumite.  The 
trials  in  France  in  many  departments  confirm  the  opinion 
already  recorded  at  the  First  International  Road  Congress 
that  they  are  only  efficient  for  a  short  time  and  that  the 
spraying  has  to  be  repeated  several  times  in  the  season. 
The  cost  per  square  yard  soon  becomes  prohibitive.  They 
are,  therefore,  " processes  de  luxe"  the  utility  of  which 
is  only  apparent  when  it  is  a  question  of  sprinkling  as  quickly 
as  possible  a  certain  length  of  road  for  a  race  or  a  procession. 
Ordinary  watering  is  very  temporary  in  its  action.  The 
methods  of  applying  have  been  greatly  improved.  Motor 
cars  fitted  with  fine  sprays  prevent  an  excess  of  water  being 
applied  and  do  the  work  very  rapidly.  Chloride  of  sodium 
dissolved  in  water  has  lasted  in  some  cases  three  or  four  days, 
but  it  is  considered  to  be  insufficiently  hydroscopic.  Chloride 
of  magnesium  and  calcium  chloride  have  a  much  greater 
affinity  for  water  than  has  sodium  chloride  and  are  con- 
sequently more  effective.  The  proportions  used  have  varied 
greatly,  so  the  results  are  very  variable.  Dust  has,  however, 
been  very  successfully  laid  in  many  localities  by  using  these 
salts.  The  writer  considers  that,  although  the  use  of  these 
salts  could  never  become  general,  they  may  be  useful  in 
many  cases. 


DUST   PREVENTION   BY   USE    OF   PALLIATIVES  95 

Germany.  SPERBER  and  GUSTAV  FRANZE.  Water 
sprinkling  is  inefficient  for  general  use  because  of  its  im- 
perfect action  and  its  very  short  life.  For  country  roads 
the  usual  necessary  long  distances  between  filling  points 
makes  water  sprinkling  costly  and  unsatisfactory. 

Calcium  chloride,  chloride  of  magnesia,  and  sea-salt 
solutions,  because  of  their  short  period  of  efficiency,  are 
usually  applicable  only  to  asphalt,  wood  or  stone  block 
pavements.  Applications  of  these  salts  must  be  made  at 
intervals  of  from  two  to  fourteen  days  depending  upon 
the  weather  and  amount  of  traffic.  These  materials  can 
be  applied  with  profit  only  in  the  municipal  watering  areas. 
Often  solutions  of  these  salts,  because  they  do  not  freeze 
readily,  are  very  good  for  sprinkling  the  roads  before 
sweeping  in  cold  weather. 

Owing  to  the  small  percentage  of  oils  sprinkled  on  the 
road,  when  emulsions  are  employed,  the  process  must  be 
repeated  frequently.  In  the  writer's  opinion  even  rich 
municipalities  cannot  use  this  process  on  extensive  areas 
of  macadam  because  of  the  high  cost  of  frequent  applica- 
tions and  consequently  must  limit  its  use  to  asphalt  and 
wooden  pavements. 

Hungary.  ALFRED  BALLO.  As  hygroscopic  salts 
failed  to  give  good  results,  the  Office  of  Public  Cleanliness 
made  numerous  experiments  with  oils.  Unrefined  petroleum 
was  considered  too  inflammable  and  odorous.  A  petro- 
leum by-product,  called  "blue  oil,"  which  gave  still  better 
results  after  being  refined,  was  finally  selected. 

The  usual  number  of  applications  is  three,  one  in  early 
spring,  the  second  four  to  six  weeks  later  and  the  final 
application  six  to  ten  weeks  after  the  second.  The  road  is 
first  swept  and  the  material  applied,  unheated,  from  ordinary 
water-carts.  The  first  application  is  usually  2  pounds  and 


96  HIGHWAY   ENGINEERING 

the  other  two  one-half  that  amount.  The  cost  is  found  to 
be  only  slightly  in  excess  of  that  for  watering. 

Norway.  J.  SKOUGAARD.  The  maintenance  of  roads 
has  not  developed  parallel  with  the  construction  of  roads. 
Sprinkling  tar  and  oil  on  the  road  surfaces  is  altogether  too 
costly  at  present  for  general  use  and  the  need  for  such 
treatment  has  not  been  keenly  felt  where  cleaning  has  been 
properly  done. 

United  States.  JOHN  R.  RABLIN.  The  use  of  calcium 
chloride  for  laying  the  dust  has  proved  satisfactory  on  a 
number  of  shaded  roads  which  are  used  exclusively  by  light 
horse  drawn  vehicles.  One  application  about  every  four 
weeks  was  required.  On  roads  where  there  is  considerable 
motor  vehicle  traffic,  the  use  of  calcium  chloride  did  not 
prevent  the  automobiles  from  disintegrating  the  surface  and 
in  a  short  time  the  roads  would  require  resurfacing 


CHAPTER  X 

BITUMINOUS  SURFACES 

BRADACZEK,  THEODOR,  Imperial  Commissioner  of  Public 
Works,  Prague,  Austria. 

CORAZZA,  CESARE,  Engineer,  Turin,  Italy. 

CROSBY,  WALTER  W.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer 
to  the  Maryland  Geological  and  Economic  Survey,  Baltimore, 
Maryland,  U.  S.  A. 

DRUMMOND,  ROBERT,  County  Surveyor,  Renfrewshire, 
Paisley,  Scotland,  Great  Britain. 

ETIER,  PAUL,  Councilor  of  State,  Lausanne,  Switzerland. 

FLETCHER,  AUSTIN  B.,  M.  Am.  Soc.  C.  E.,  Secretary, 
Massachusetts  Highway  Commission,  Boston,  Massachusetts, 
U.  S.  A. 

FRANZE,  GUSTAV,  Commissioner  of  Public  Works,  Frank- 
fort-on-the-Main,  Germany. 

FROIDURE,  EUGENE,  Principal  Engineer  of  Bridges  and 
Roads,  Ypres,  Belgium. 

HOOKER,  S.  PERCY,  Chairman,  New  York  Highway 
Commission,  Albany,  New  York,  U.  S.  A. 

LE  GAVRIAN,  P.,  Engineer  of  Bridges  and  Roads,  Ver- 
sailles, France. 

RABLIN,  JOHN  R.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer, 
Metropolitan  Park  Commission,  Boston,  Massachusetts, 
U.  S.  A. 

97 


98  HIGHWAY    ENGINEERING 

Ross,  CHARLES  W.,  Street  Commissioner,  Newton, 
Massachusetts,  U.  S.  A. 

SCHLAEPFER,  ARTHUR,  Street  Inspector,  Zurich,  Switzer- 
land. 

SPERBER,  Chief  Engineer,  Hamburg,  Germany. 

TEDESCHI,  MASSIMO,  Engineer,  Turin,  Italy. 

VERSTRAETE,  RICHARD,  Engineer  of  Bridges  and  Roads, 
Bruges,  Belgium. 

WENNER,  VICTOR,  City  Engineer,  Zurich,  Switzerland. 

WYNNE-ROBERTS,  R.  O.,  M.  Inst.  C.  E.,  F.  R.  San.  Inst., 
Westminster,  London,  England,  Great  Britain. 

Austria.  THEODOR  BRADACZEK.  Based  on  the  funda- 
mental principle  that  the  tar  macadam  system  of  road 
construction  is  almost  as  expensive  but  is  not  as  durable 
as  that  with  basalt  or  granite  kleinpflaster,  we  in  Bohemia 
have  concerned  ourselves  only  with  surface  tarring,  and  have 
confined  it  to  stretches  which  are  subject  to  traffic  of  light 
vehicles  and  automobiles,  such  as  those  of  the  roads  con- 
necting the  two  watering-places,  Karlsbad  and  Marienbad. 

Belgium.  EUGENE  FROIDURE  and  RICHARD  VER- 
STRAETE. Crude  tar  direct  from  the  gas  houses  is  employed 
for  surface  tarring.  This  tar  was  obtained  at  a  cost  of 
$4.82  per  ton  in  1909.  The  results  attained  vary  con- 
siderably, although  as  a  rule  the  dust  is  satisfactorily  laid. 

Surface  tarring  is  done  both  by  machine  and  by  hand. 
The  type  of  machine  usually  employed  for  spreading  the 
tar  is  a  watering-cart  fitted  with  mechanical  brushes  and 
hauled  behind  a  steam  roller.  The  roller  is  fitted  with  a 
tank  for  heating  the  tar.  The  tar  flows  from  the  heating 
tank  to  the  watering-cart,  from  which  it  is  sprinkled  on  the 


BITUMINOUS   SURFACES  99 

road.  The  road  is  previously  swept  by  horse  sweepers. 
The  average  amount  of  tar  used  by  the  machine  method  is 
0.23  of  a  gallon  per  square  yard,  the  total  cost  being  about 
0.73  cents. 

Where  hand  work  is  employed  the  amount  of  tar  used 
is  0.19  of  a  gallon  per  square  yard  and  the  total  cost  is  about 
0.66  cents.  It  is  cheaper  than  the  machine  method  princi- 
pally because  the  deterioration  of  machinery  is  a  fairly 
large  item.  The  hand  method  has  several  advantages  to 
recommend  it  besides  low  cost.  There  is  no  apparatus  to 
get  out  of  order,  ordinary  workmen  may  be  employed,  and 
the  method  offers  less  inconvenience  to  traffic  because  the 
top  dressing  may  be  kept  close  up  to  the  edge  of  the  tarred 
area.  The  chief  advantage  of  the  machine  method  is  speed. 

France.  P.  LE  GAVRIAN.  Superficial  tarring  has 
increased  noticeably  in  France  of  late  years.  Spreading  or 
spraying  the  tar  is  accomplished  by  means  of  hand  sprin- 
klers or  by  machines  consisting  of  tanks  on  wheels  with 
brushes  attached.  The  tar  is  generally  heated  to  100 
degrees  Centigrade,  but  in  a  number  of  localities  cold  tar 
is  rendered  fluid  by  adding  10  per  cent  of  heavy  oil.  The 
average  amount  of  tar  used  for  the  first  application  is  about 
J4  of  a  gallon  per  square  yard  and  subsequent  applications 
are  made  with  less  quantity. 

The  method  of  burning  the  tar,  after  it  has  been  spread 
on  the  roads,  has  been  tried  in  several  places  but  has  not 
been  generally  adopted.  Tar  in  the  form  of  powder  has  been 
applied  in  some  cases. 

The  life  of  surface  tarring  is  dependent  so  largely  upon 
climate,  quality  of  materials,  and  amount  of  traffic  that  the 
writer  does  not  draw  conclusions  on  this  point.  The 
majority  of  engineers  consulted  were  of  the  opinion  that  the 


100  HIGHWAY   ENGINEERING 

process  should  be  done  yearly.  The  writer  believes,  with- 
out committing  himself  to  figures,  that  in  a  dry  season  the 
life  of  a  road  is  sensibly  lengthened  by  tarring,  and  that 
in  a  wet  season  tarring  preserves  the  road  as  long  as  the  road 
surface  is  not  destroyed  by  the  combined  action  of  traffic 
and  rain.  These  conclusions  hold,  however,  only  up  to  a 
certain  amount  of  traffic,  since,  when  this  amount  is  exceeded, 
mud  is  formed  just  the  same  as  on  non-treated  roads.  Where 
this  limit  of  traffic  is  greatly  exceeded  this  tarry  mud, 
stirred  up  and  churned  by  the  wheels  of  vehicles,  never  dries 
and  becomes  an  element  of  disintegration. 

Germany.  SPERBER  and  GUSTAV  FRANZE.  As  a  rule 
there  are  no  specifications  for  the  tars  to  be  employed, 
although  it  is  recognized  that  they  should  be  freed  as  much 
as  possible  from  water  and  ammonia  without  removing  the 
volatile  oils.  Liquid  oils,  creosote  oils,  and  petroleum 
distillates  are  sometimes  employed  to  thin  the  tar.  Crude 
gas  tar  is  the  material  most  frequently  used,  although 
refined  tar  has  been  employed  to  a  limited  extent.  The 
road  surface  should  be  warm,  somewhat  porous,  and  per- 
fectly dry  in  order  to  secure  good  results.  The  roads  are 
first  well  cleaned  and  the  heated  tar  is  then  applied  by  hand 
or  machine.  Many  towns  recommend  surface  tarring  to 
be  applied  to  macadam  roads  from  six  to  eight  weeks  after 
construction  in  order  to  secure  the  best  results.  Sand  is 
generally  used  as  a  top  dressing,  although  stone  dust  and 
roadside  dust  are  employed  in  some  cases.  Most  towns 
open  the  road  immediately  after  treatment;  and  they 
prefer  machine  tarring  to  hand  tarring  because  of  the 
greater  rapidity  and  uniformity  of  the  work.  One  horse 
drawn  tarring  machine  will  cover  from  3,600  to  7,800  square 
yards  of  surface  in  a  day  of  ten  to  fourteen  working  hours. 


BITUMINOUS    SURFACES  101 

The  majority  of  towns  consider  rolling  necessary.  The 
average  cost  per  square  yard  of  the  hand  surface  tarring  is 
4  cents  and  of  machine  tarring  is  3.2  cents.  Subsequent 
applications  may  be  done  at  somewhat  less  expense.  Most 
towns  state  that  tarring  is  cheaper  than  watering.  The  life 
of  the  first  tarring  is  stated  to  be  about  one  year.  Under 
severe  traffic  the  period  of  wear  is  reduced  to  about  one-half 
year.  Wet  weather  and  shady  location  are  two  conditions 
mentioned  as  being  injurious  to  surface  tarred  roads. 

Great  Britain.  ROBERT  DRUMMOND.  With  regard  to 
the  general  tendencies  of  practice  in  Scotland,  the  following 
statements  may  be  of  interest.  In  populous  districts  the 
new  macadam  surfaces  are  either  bound  with  tarred  chip- 
pings  or  with  a  tar  composition  applied  by  means  of  a  spray- 
ing machine. 

Ordinary  surface  tarring  has  been  found  effective  for 
one  year  on  roads  subjected  to  heavy  traffic  and  for  a  longer 
time  on  roads  with  lighter  traffic.  The  cost  of  superficial 
tarring,  exclusive  of  the  cost  of  sweeping  and  sanding,  is 
from  1J/2  cents  to  2  cents  per  superficial  yard.  The  method 
of  resurfacing  with  tarred  chips  is  as  follows:  the  road  to 
be  repaired  is  first  scarified,  new  metal  is  applied  and  the 
road  is  rolled  until  a  hard  and  smooth  surface  is  obtained; 
then  without  the  use  of  water  a  coating  of  tarred  chippings 
is  applied,  rolled  and  sprinkled  with  dry  chippings  during 
the  process  of  rolling.  The  addition  of  dry  screenings  dur- 
ing the  final  rolling  facilitates  the  rolling  and  also  gives  a 
finished  surface,  which  at  once  allows  the  traffic  to  pass  over 
the  road.  The  additional  cost  of  binding  with  tarred  basalt 
or  whinstone  chippings  is  2  cents  per  superficial  yard. 

Great  Britain.  R.  O.  WYNNE-ROBERTS.  Before  old 
road  surfaces  are  tarred  all  pot  holes  should  be  repaired. 


.  _  I. . 

.«UV*i 

102  HIGHWAY   ENGINEERING 

The  dust  should  be  brushed  off,  leaving  the  joints  between 
the  stones  exposed  as  much  as  possible.  The  road  should 
be  dry  and  warm  as  damp  surfaces  chill  the  tar  and  reduce 
the  penetration.  The  tar  can  be  distributed  either  by  hand 
or  by  machine,  the  latter  method  being  much  more  rapid, 
but  brooming  may  have  to  be  resorted  to  with  either  method 
to  prevent  the  tar  from  ponding.  Time  should  be  given  the 
tar  to  soak  into  the  surface  until  a  durable  and  plastic  skin 
is  formed,  and  during  this  time  traffic  should  be  diverted 
from  the  road.  Covering  the  tarred  surface  immediately 
with  sand  or  chips  does  not  seem  warranted,  but  if  such  a 
covering  is  used,  it  should  be  a  light  one  and  evenly  spread. 
It  is  useless  to  tar  roads  built  on  a  wet  subsoil  that  is  not 
efficiently  drained.  Refined  tar  is  preferable  to  crude  tar 
because  it  is  free  from  water  and  light  oils,  is  more  uniform 
in  quality,  is  more  lasting,  and  if  applied  hot  it  will  not 
peel  from  dry  stone  surfaces. 

Italy.  MASSIMO  TEDESCHI,  and  CESARE  CORAZZA. 
Surface  tarring  has  been  used  to  a  considerable  extent  in 
Jtaly.  The  first  trials  of  this  method  were  carried  out  in 
1901  at  Lugo,  while  in  1902  the  Province  of  Turin  com- 
menced surface  tarring,  which  process  of  laying  dust  has 
been  continued  there  until  the  present  time.  Surface 
tarring  has  been  uniformly  successful  in  laying  dust  and  in 
preserving  the  road  surface.  In  sections  exposed  to  violent 
winds,  which  rendered  the  maintenance  of  ordinary  macadam 
a  difficult  problem,  the  application  of  tar  has  been  found 
to  be  very  effective.  The  cost  of  surface  tarring  in  Italy 
varies  from  1.6  cents  to  3.2  cents  per  square  yard. 

Switzerland.  PAUL  ETTER.  Tarring  is  the  sole  means 
employed  to  cope  with  dust.  Surface  tarring  is  considered 
short-lived  on  roads  where  the  traffic  is  excessive,  because 


BITUMINOUS   SURFACES  103 

it  cannot  prevent  internal  dislocation.  The  first  tar  spray- 
ing is  estimated  to  cost  about  $300  per  mile  for  a  20  foot 
road,  and  subsequent  annual  renewals  cost  in  the  neighbor- 
hood of  $100  per  mile,  the  lower  cost  being  due  in  part  to 
the  lessened  cost  of  sweeping  and  cleaning. 

Switzerland.  VICTOR  WENNER  and  ARTHUR  SCHLAE- 
PFER.  In  order  that  surface  tarring  may  be  successful  it  is 
necessary  that  the  roads  to  be  so  treated  be  either  in  a  very 
good  state  of  preservation  or  previously  resurfaced  with 
new  stone.  The  proper  time  for  the  application  of  the  tar 
coating  is  from  four  to  six  weeks  after  the  rolling  of  the  new 
surfacing.  It  is  essential,  in  all  cases,  that  the  surface  be 
perfectly  dry  and  free  from  dirt  or  dust  and  that  the  tar  to  be 
used  should  be  as  free  as  possible  from  water  and  ammonia. 
The  first  coating  of  tar  should  be  applied  only  during  dry 
weather,  and,  if  possible,  after  several  warm,  sunny  days. 
For  a  second  coating  a  long  period  of  warm  weather  previous 
to  tarring  is  not  so  essential.  Before  the  tar  coating  has 
become  quite  hard,  it  should  be  covered  with  a  coarse  sand 
and  then  rolled  with  a  hand  roller. 

United  States.  WALTER  W.  CROSBY.  In  1907  the 
City  of  Annapolis  employed  Tarvia  on  about  8,600  square 
yards  of  street  surface.  The  macadam  was  laid  in  exactly 
the  same  manner  as  if  it  were  ordinary  water  bound  con- 
struction. After  thoroughly  rolling  and  watering  the  sur- 
face was  left  to  dry.  Then  the  macadam  was  well  swept, 
and  heated  Tarvia  was  applied  through  a  hose  and  spread 
by  means  of  hand  brooms,  a  wave  of  material  being  pushed 
over  the  surface.  About  J^  gallon  of  Tarvia  per  square  yard 
was  used.  Later  the  absorbent  spots  were  filled  with 
enough  additional  bituminous  material  to  give  a  uniform 
coating  of  J£  °f  an  inch  over  the  niacadam.  A  1  inch  coating 


104  HIGHWAY   ENGINEERING 

of  chips,  34  of  an  mcn  to  %  of  an  inch  in  the  longest  dimen- 
sions, was  then  spread  evenly  over  the  tarred  surface  and 
rolled.  The  surface  later  presented  an  appearance  similar 
to  an  asphalt  pavement.  There  was  no  dust  except  when 
the  removal  of  foreign  matter  brought  on  by  the  traffic  was 
delayed.  This  treatment  gave  excellent  results  for  about 
two  years,  at  which  time  another  light  application  of  Tarvia 
was  made  in  a  similar  manner.  It  is  hoped  that  this  last 
application  will  last  longer  than  the  first.  The  penetration 
of  the  tar  into  the  macadam  appeared  to  be  from  1J^  to  2 
inches. 

Later,  work  along  the  same  lines  gave  either  similar  or 
better  results.  Considerable  difficulty  was  encountered  in 
securing  a  satisfactory  bituminous  material,  the  main  defect 
of  most  of  these  refined  tars  being  the  tendency  to  lose  their 
life  and  become  brittle  at  too  early  a  period. 

United  States.  AUSTIN  B.  FLETCHER.  In  1908  and 
1909  a  number  of  miles  of  State  Highway  were  treated  by 
the  penetration  method  or  by  the  mixing  method.  The 
work  seemed  to  demonstrate  that  a  sealing  coat  of  bitumi- 
nous material  was  necessary  in  both  methods.  Both  of  these 
methods  were  too  expensive  for  extensive  work  in  resur- 
facing old  roads,  and  so  the  Commission  adopted  on  a 
large  scale  the  process  of  surface  treatment.  The  road  is  first 
patched  and  rolled  to  secure  as  true  and  even  a  surface  as 
possible.  All  the  surplus  dust  is  then  swept  off,  usually 
with  horse  drawn  sweepers,  and  the  exposed  surface  is 
cleaned  as  well  as  possible.  The  bituminous  material  is 
applied  by  gravity  distributors  or  by  spraying  machines 
at  a  rate  of  J^  to  ^  of  a  gallon  per  square  yard.  A  coat  of 
sand,  screened  gravel,  or  stone  screenings  is  immediately 
spread  over  the  surface  to  absorb  the  surplus  bituminous 


BITUMINOUS    SURFACES  105 

material  and  the  roadway  is  rolled  with  a  steam  roller.  In 
1909,  1,050,000  square  yards  were  treated  by  this  method 
at  an  average  cost  of  6  cents  per  square  yard,  using  an 
average  of  0.312  of  a  gallon  of  bituminous  material  per 
square  yard.  In  all  of  the  work  so  done  about  90  per  cent 
of  the  bituminous  material  used  was  an  asphaltic  oil,  con- 
taining about  80  per  cent  of  asphalt. 

The  refined  tars  supplied  under  specifications  seem  to 
have  been  uniformly  good,  and  the  specifications  appear  to 
be  open  to  less  question  than  those  for  asphaltic  oil. 

It  is  probable  that  at  least  one  more  year  will  need  to 
elapse  before  it  can  be  said  conclusively  that  protective 
coatings  of  bituminous  material  as  herein  described  will 
protect  the  roads  at  a  reasonable  cost.  Such  work  as  the 
Commission  has  already  done  during  1908  and  1909,  how- 
ever, seems  to  indicate  that  at  least  a  partial  solution  of 
the  problem  has  been  reached  by  that  process.  There  seems 
to  be  little  doubt  that  a  coating,  when  not  less  than  J/£  of 
a  gallon  per  square  yard  of  bituminous  material  is  used, 
will  last  for  two  years  with  small  expense  for  repairs  under 
the  traffic  conditions  to  which  the  Massachusetts  State 
Highways  are  now  subjected. 

The  tars  and  the  asphaltic  oils  appear  to  have  given 
equally  good  results  as  protectors  but  it  should  be  stated 
that  the  tar  forms  a  much  harder  coating  than  does  the  oil, 
and  one  which  is  likely  to  be  more  slippery.  In  fact,  there 
have  been  some  complaints  received  that  tarred  roads  are 
unsafe  for  horses.  It  is  also  apparent  that  neither  tar  nor 
oil  should  be  applied  to  a  macadam  road,  the  crown  of 
which  is  in  excess  of  J^  of  an  inch  to  the  foot.  It  is  probable 
that  much  better  results  are  secured  where  the  crown  is 
not  in  excess  of  V3  of  an  inch  to  the  foot,  since  so  smooth  a 


106  HIGHWAY   ENGINEERING 

surface  as  results  from  the  use  of  either  form  of  bitumen 
requires  but  little  crown  to  shed  the  water  which  falls  upon 
the  road.  The  asphaltic  oil,  when  applied  as  before  stated, 
results  in  a  rubber-like  coating  which  gives  a  good  footing 
for  the  horses  and  which  does  not  become  slippery  except 
under  unusual  frost  conditions.  It  is  hoped  by  the  applica- 
tion of  these  surface  coatings  to  do  away  for  an  indefinite 
period  with  the  necessity  for  resurfacing  with  broken  stone. 

If  no  wear  is  permitted  to  come  upon  the  stones  them- 
selves, the  only  cost  for  maintenance  will  be  that  of  restoring 
the  surface  coating  which  ought  not,  according  to  the 
Massachusetts  experiment,  to  exceed  2.85  cents  per  square 
yard  per  year. 

United  States.  S.  PERCY  HOOKER.  Oiling  of  roads 
is  carried  out  extensively  in  the  State  of  New  York.  The 
oil  is  applied  both  cold  and  hot,  and  specifications  for  oils 
applied  by  both  methods  are  in  use.  The  surface  of  the  road 
is  brushed  clear  of  dust  and,  after  the  oil  is  applied,  it  is 
covered  with  a  ^  to  %  inch  layer  of  dustless  screenings. 
Sand  and  gravel  were  first  used  for  top  dressings,  but  they 
were  not  satisfactory.  About  100  cubic  yards  of  dustless 
screenings  are  required  to  properly  cover  a  mile  of  road 
in  this  manner  and  these  must  be  constantly  brushed  back 
into  the  center  of  the  road  by  the  patrolman  •  for  a  period 
of  three  to  four  weeks  until  compacted  by  traffic. 

Cold  oil  treatment  costs  about  $350  per  mile,  the  oil 
costing  from  4  to  5J/2  cents  per  gallon,  and  from  3,500  to 
4,000  gallons  being  used.  Although  none  of  the  roads  treat- 
ed in  this  manner  have  gone  through  a  winter,  the  writer 
thinks  that  the  second  year  treatment  will  require  less  oil 
than  the  first,  and  that  after  three  or  four  years,  a  treat- 
ment for  one  year  might  be  omitted  entirely. 


BITUMINOUS   SURFACES  107 

Hot  oiling  was  done  with  an  Aitken's  machine  and  one 
manufactured  in  New  York.  The  comparative  cost  of 
applying  hot  oil  is  increased  by  the  greater  cost  of  the 
machine  with  which  the  oiling  is  done.  When  hot  oil  has 
been  applied  upon  a  newly  finished  road  bed  it  forms  a 
blanket  that  may  be  lifted  away  from  the  surface  unless 
the  screenings  have  first  been  thoroughly  brushed  from  the 
road,  leaving  the  stones  in  the  top  course  exposed.  The 
writer  considers  that  two  applications  of  cold  oil  upon 
successive  years  will  cost  approximately  the  same  as  one 
application  of  hot  oil  and  will  be  more  satisfactory. 

The  writer  also  believes  that  there  is  a  tendency  on 
the  part  of  any  tar  product,  when  used  on  the  road  surface, 
to  harden  and  cake,  leaving  a  crust  which  is  not  a  con- 
stituent part  of  the  road.  This  crust  will  break  through  in 
places  and  will  not  heal,  since,  after  hardening  once,  a  tar 
product  seems  to  lose  its  elasticity  and  stickiness. 

United  States.  JOHN  R.  RABLIN.  Gravel  roads,  in 
the  construction  of  which  a  clay  binder  has  been 
used,  have  been  built  extensively  for  the  parkway  drives. 
They  have  given  very  good  satisfaction  except  that, 
at  the  season  of  the  year  when  the  frost  is  coming  out  of 
the  ground,  they  are  liable  to  rut  if  the  amount  of  clay 
binder  is  at  all  excessive.  To  overcome  this  objection  and 
to  retain  the  gravel  surfaced  type  of  roads  for  the  parkways, 
the  writer  has  been  using  for  the  last  two  years  a  crushed 
stone  base  about  4  inches  in  thickness  with  a  2^  to  3  inch 
layer  of  binding  gravel  on  top.  After  the  completion  of  the 
surface  and  before  it  has  become  too  hard  to  readily  absorb 
the  material,  a  treatment  of  heavy .  asphaltic  oil,  about  1 
gallon  per  square  yard,  is  applied,  which  serves  to  make  the 
surface  dustless  and  in  a  large  measure  to  preserve  it.  The 


108  HIGHWAY   ENGINEERING 

most  suitable  oil  to  be  used  has  been  determined  by  the 
actual  use  of  various  grades  of  oil  on  the  roads.  The  writer 
believes  that  on  roads  having  a  light  traffic,  including  auto- 
mobiles, one  application  every  two  years  will  suffice  and  that 
on  roads  having  a  fairly  heavy  traffic  an  application  may  be 
required  each  year. 

A  large  portion  of  the  macadam  roads  of  the  park 
system  have  been  treated  with  a  surface  application  of 
refined  tar,  which  has  served  to  protect  them  and  keep  them 
in  good  condition  up  to  the  present  time,  whereas  otherwise 
they  would  have  been  destroyed.  One  objection  to  this 
treatment  with  tar  is  its  slipperiness  for  horses  in  cold 
weather,  but  by  the  use  of  coarse,  sharp  stone  screenings 
up  to  %  of  an  inch  in  size  with  the  tar  coating,  this  is  over- 
come to  a  large  degree. 

United  States.  CHARLES  W.  Ross.  The  writer  has 
found  that  a  heavy  asphaltic  oil  worked  into  the  surface 
of  the  road  prolongs  the  life  of  the  road,  makes  it  dustless, 
free  from  mud,  and  non-slippery.  Before  the  oil  is  applied 
it  is  thoroughly  mixed  with  sand  heated  from  150  degrees  to 
175  degrees  Fahrenheit,  the  proportions  used  being  1  cubic 
foot  of  sand  to  1  gallon  of  heavy  asphaltic  oil.  The  mixture 
is  then  spread  on  the  street  with  shovels,  raked  with  a 
f ourteen-tooth  wooden  lawn  rake  and  allowed  to  be  compact- 
ed by  traffic.  During  the  construction  of  the  surface  it  is 
not  necessary  to  close  the  streets.  It  has  proved  very 
satisfactory  and  one  treatment  a  year  seems  to  be  sufficient. 
After  the  first  year  the  expense  is  much  less,  as  the  material 
has  worked  into  the  surface  of  the  road  making  it  nearly 
waterproof. 


CHAPTER  XI 
BITUMINOUS  PAVEMENTS] 

BLANCHARD,  ARTHUR  H.,  M.  Am.  Soc.  C.  E.,  Deputy  En- 
gineer, Rhode  Island  State  Board  of  Public  Roads,  Providence, 
R.  L,  U.  S.  A. 

BREDTSCHNEIDER,  AUGUST,  Commissioner  of  Public 
Works,  Charlottenburg,  Germany. 

CATTANEO,  PAOLO,  Engineer,  Office  of  Municipal  En- 
gineer, Milan,  Italy. 

CROMPTON  COL.  R.  E.,  M.  Inst.  C.  E.,  Royal  Automobile 
Club,  London,  England,  Great  Britain. 

CROSBY,  WALTER  W.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer 
to  the  Maryland  Geological  and  Economic  Survey,  Baltimore, 
Maryland,  U.  S.  A. 

DE  JAEGERE,  ALBERIC,  Civil  Engineer,  Antwerp,  Bel- 
gium. 

DRUMMOND,  ROBERT,  County  Surveyor,  Renfrewshire, 
Paisley,  Scotland,  Great  Britain. 

EISENLOHR,  Director,  Board  of  Public  Works,  Strasburg, 
Germany. 

FLECK,  GEORG,  Commissioner,  Board  of  Public  Works, 
Dresden,  Germany. 

FRANZE,  GUSTAV,  Commissioner  of  Public  Works, 
Frankfort-on-the-Main,  Germany. 

HENNING,  JOHN,  Imperial  Commissioner  of  Public 
Works,  Oberlahnstein-on-the-Rhine,  Germany. 

109 


1.10  HIGHWAY   ENGINEERING 

HORBURGER,  Member,  Board  of  Public  Works,  Munich, 
Germany. 

LE  GAVRIAN,  P.,  Engineer  of  Bridges  and  Roads,  Ver- 
sailles, France. 

PARKER,  HAROLD,  M.  Am.  Soc.  C.  E.,  Chairman, 
Massachusetts  Highway  Commission,  Boston,  Massachusetts, 
U.  S.  A. 

PINE,  JAMES  A.  W.,  Consulting  Engineer,  New  York 
City,  U.  S.  A. 

RABLIN,  JOHN  R.,  M.  Am.  Soc.  C.  E.,  Chief  Engineer, 
Metropolitan  Park  Commission,  Boston,  Massachusetts, 
U.  S.  A. 

SAUNIER,  HONORE,  District  Inspector,  Rouen,  France. 

SCHLAEPFER,  ARTHUR,  Street  Inspector,  Zurich,  Switzer- 
land. 

SPERBER,  Chief  Engineer,  Hamburg,  Germany. 

WARREN,  GEORGE  C.,  President,  Warren  Bros.  Co., 
Boston,  Massachusetts,  U.  S.  A. 

WENNER,  VICTOR,  City  Engineer,  Zurich,  Switzerland. 

Belgium.  ALBERIC  DE  JAEGERE.  The  method  of 
laying  asphalt  pavements  does  not  differ  essentially  from 
the  method  employed  in  France  and  Germany.  Powdered 
rock  asphalt  is  the  usual  material  employed.  The  average 
cost  including  the  concrete  foundations  is  $2.59  to  $2.74 
per  square  yard. 

France.  P.  LE  GAVRIAN.  There  has  been  little  tar 
macadam  constructed  in  France.  There  is,  however,  about 
to  be  undertaken  on  a  large  scale  the  commercial  manu- 
facture of  tarred  material.  The  results  from  the  trials  with 


BITUMINOUS   PAVEMENTS  111 

tar  macadam  constructed  with  various  road  metals  have 
given  mediocre  results.  Tar  macadam,  while  undoubtedly 
more  costly  than  poured  macadam,  will  always  have  the 
advantage  over  the  latter  in  that  the  tar  is  more  evenly 
distributed  between  the  stones  thus  giving  homogeneity, 
which  quality  is  of  paramount  importance  to  all  good  roads. 

A  process  known  as  pitch  macadam  has  been  employed. 
This  method  consists  of  mixing  pitch  and  sand  together  and 
spreading  this  mixture  on  the  road  during  the  process  of 
compacting  and  later  applying  oil  to  reduce  the  pitch  to  a 
kind  of  tar.  The  trials  were  too  recent  for  the  formation 
of  any  definite  opinion  as  to  the  merits  of  the  process, 
although  borings  showed  that  the  oil  had  penetrated  %  of 
an  inch  to  1^4  inches  and  had  made  the  pitch  more  or  less 
plastic.  The  process  only  costs  from  6^/2  cents  to  9J^  cents 
per  square  yard  above  the  cost  of  ordinary  macadam. 

A  combination  of  tar,  soap  and  clay  mixed  with  the 
road  metalling  before  rolling  has  given  only  mediocre  re- 
sults. 

Tarvia,  a  patented  English  product,  has  been  employed 
by  spreading  a  hot  mixture  of  fine  gravel  and  Tarvia  over 
the  old  road,  covering  this  layer  with  the  road  metal,  and 
later  applying  another  Tarvia  mixture.  At  the  time  of 
writing  the  results  could  not  be  ascertained  definitely. 

Trials  made  of  placing  metalling  on  tar,  previously 
applied  cold  to  the  surface  of  old  roads,  have  not  proved  to 
be  superior  to  ordinary  surface  tarring. 

Tar  has  been  t  applied  by  the  penetration  method  both 
in  a  single  process  and  by  the  application  of  several  layers 
of  tar,  good  results  having  as  a  rule  ensued. 

The  writer  has  employed  a  system  consisting  of  small^bro- 
ken  porphyritic  stone  varying  from  %  of  an  inch  to  1^2  inches 


112  HIGHWAY  ENGINEERING 

in  dimensions  coated  with  a  mastic  of  asphalt  and  sand, 
and  spread  in  a  layer  of  1J^  inches  to  2  inches  in  thickness. 
In  this  manner  a  very  close  grained  macadam  is  obtained, 
the  interstices  of  which  are  filled  with  mastic.  The  applica- 
tion was  made  in  August,  1909,  in  Versailles  upon  the  road 
to  Paris  where  there  is  a  very  heavy  horse  drawn  vehicle 
traffic,  composed  chiefly  of  the  household  refuse  carts  going 
to  the  road  depots  of  the  city. 

The  results  have  been  excellent,  both  in  winter  and  in 
summer.  The  frosts,  it  is  true,  were  not  severe  last  winter 
and  have  not  damaged  in  any  way  the  asphalt  surfacing, 
which  has  maintained  itself  up  till  now  in  a  perfect  condition, 
whereas  the  metalled  and  tarred  sections  of  the  roads  have 
suffered  during  the  bad  weather.  The  results  have  been  so 
encouraging  that  the  Minister  of  Public  Works  has  author- 
ized the  continuation  of  the  trials  and  has  granted  the 
writer  the  necessary  funds  for  this  purpose.  A  new  applica- 
tion will  be  made  this  month.  According  to  the  preliminary 
trials,  with  which  the  author  has  been  occupied  lately  with 
a  view  to  ascertaining  the  quantities  and  to  improving  the 
methods  of  construction,  he  has  arrived  at  this  conclusion: 
that  this  macadam  laid  as  a  bed  2  inches  in  thickness  will 
not  cost  more  than  64  cents  to  72  cents  per  square  yard  with 
the  materials  in  our  district,  the  porphyritic  stone  costing 
$2.97  per  cubic  yard  and  the  asphalt  mastic  costing  $14.00 
to  $15.75  per  ton.  If  the  good  results  attained  up  till  now 
are  confirmed,  a  road  surfacing  will  have  been  obtained 
intermediate  between  the  macadam  and  the  stone  block 
pavement  both  as  regards  resistance  and  price. 

France.  HONORE  SAUNIER.  The  following  experi- 
ments with  the  Bedeau  system  of  construction  were  carried 
out.  Several  days  before  the  laying  on  the  road,  stone, 


BITUMINOUS   PAVEMENTS  113 

clay  and  tar  were  mixed  in  proportions  of  three  wheel- 
barrows of  stone,  one  wheelbarrow  of  clay,  and  2.9  gallons 
of  tar.  The  stones  were  wet  previous  to  mixing  with  clay. 
After  consolidating  this  coating  by  rolling,  a  surface  coat 
of  tar  was  applied.  The  appearance  of  the  road  after 
completion  was  not  different  from  that  of  ordinary  macadam. 
In  another  experiment  galgatine  (tar  and  clay  mixed  in 
barrels  in  a  proportion  two  to  one,  with  a  little  water)  was 
brought  to  the  road  and  mixed  with  stone  in  the  proportion 
one  to  twelve.  Sand  and  cement  made  into  a  mortar  was 
then  mixed  with  the  coated  stone.  This  product  was  laid 
much  the  same  as  in  the  previous  experiment  except  that  a 
coating  of  sand  was  added  instead  of  the  tar  coating.  The 
road  has  always  been  muddy  since  construction.  Appar- 
ently this  system  is  not  to  be  recommended. 

Germany.  JOHN  HENNING.  During  the  past  two 
years  about  135,000  square  yards  of  bituminous  pavement 
have  been  laid.  Machine  mixing  has  been  found  to  be  the 
only  method  of  work  which  assures  good  construction. 
Six  different  types  of  mixing  machines,  including  both 
batch  mixers  and  continuous  mixers,  are  used  in  Ger- 
many. 

Germany.  SPERBER  and  GUSTAV  FRANZE.  For  suc- 
cessful construction  by  the  mixing  method,  the  road  metal 
should  be  perfectly  dry  and  warm,  the  tar  should  be  hot, 
and  the  process  should  be  carried  out  only  in  dry  weather. 
This  method  of  construction  is  not  used  extensively  in 
Germany,  but  some  of  the  trials  are  interesting.  The 
material  employed  is  usually  refined  tar  or  tar  mixed  with 
a  certain  amount  of  asphalt  cement.  Poor  results  by  this 
method  are  often  obtained  due  to  rolling  while  the  tar  is 
wet  or  after  it  has  set  up.  Realizing  this,  Aeberli  has  de- 


114  HIGHWAY   ENGINEERING 

vised  a  method  of  making  tar  take  the  form  of  soft  pitch. 
The  following  is  a  description  of  this  method. 

The  perfectly  dry  and  well  heated  road  metal  is  com- 
pletely impregnated  with  hot  coal  tar  (Aeberli  states  35 
degrees  to  40  degrees  Centigrade),  and  is  then  placed  in 
heaps  and  well  covered  with  sand.  The  road  metal  is 
allowed  to  remain  in  this  condition  for  about  three  weeks. 
During  this  time  the  soft  pitch  referred  to,  which  possesses 
very  great  adhesion,  is  formed.  A  layer  of  pitch  coated 
road  metal  3  inches  to  5J^  inches  thick  is  then  well  rolled 
and  exposed  for  three  or  four  days  to  the  action  of  the  air 
and  sun.  During  this  time  hard  pitch  is  formed,  so  that  a 
thoroughly  close  and  firm  layer  of  road  metal  is  obtained 
owing  to  the  faces  of  the  stone  adhering  firmly  one  to  another 
and  to  the  soft  pitch  hardening  into  hard  pitch.  Aeberli 
then  rolls  on  this  bed  of  road  metal  a  moderately  thick 
layer  of  small  stone  1%  inches  to  2  inches  in  size,  treated  in 
a  similar  manner.  Exceedingly  good  results  have  been 
obtained  with  this  method,  and  it  would  be  well  to  test  it 
on  a  larger  scale. 

The  so-called  penetration  method  has  been  employed 
frequently,  although  the  general  opinion  seems  to  be  that 
surface  tarring  after  six  or  eight  weeks  is  fully  as  good, 
provided  the  traffic  is  not  too  severe. 

The  stone  has,  in  a  few  cases,  been  mixed  with  bitu- 
minous material  on  a  mixing  board  or,  as  in  one  case,  by 
employing  a  concrete  mixer.  In  two  towns  coating  the  road 
metal  has  been  accomplished  by  submerging  hot  stone  in 
cold  tar,  while  in  other  cases,  cold  stone  has  been  submerged 
in  hot  tar. 

Germany.  AUGUST  BREDTSCHNEIDER;  HORBURGER; 
EISENLOHR  and  GEORG  FLECK.  The  material  employed  in 


BITUMINOUS   PAVEMENTS  115 

the  construction  of  asphalt  pavements  is  generally  a  ground 
bituminous  limestone  containing  between  9  and  13  per 
cent  of  bitumen.  The  asphalt  surface  is  laid  on  a  concrete 
bed  about  10  inches  thick.  Old  asphalt  pavement  has 
recently  been  reground  and  mixed  with  sand  and  Trinidad 
asphalt  to  form  a  new  wearing  surface.  This  method  is 
stated  to  be  comparatively  inexpensive. 

A  pavement  consisting  of  slabs  of  from  1^  inches  to  2 
inches  in  thickness  with  faces  from  6  inches  to  8  inches 
square,  made  of  asphalt  powder  under  heavy  pressure,  has 
been  in  use  for  a  considerable  time  in  the  west  and  south  of 
Germany.  The  plates  are  laid  in  cement  mortar  or  bitumen 
on  a  smooth  concrete  bedding  8  inches  thick.  Slab  pave- 
ment of  this  kind  laid  on  the  carriageway  behaves  much  like 
a  rammed  asphalt  pavement.  In  some  of  the  south  German 
towns  use  is  being  made  experimentally  of  vulkanos  slab 
pavement  consisting  of  hard  stone  metalling  and  a  suitable 
cement  which  is  subjected  to  high  pressure  and  a  twelve 
day  burning  process.  The  slabs  are  about  3  inches  thick 
by  10  inches  square,  and  are  laid  in  cement  mortar  on  the 
concrete  base. 

Great  Britain.  COL.  R.  E.  CROMPTON.  The  method 
of  laying  a  graded  aggregate  mixed  with  tar,  the  writer  con- 
siders superior  to  surface  tarring  and  is  a  method  bound  to 
become  common  in  England.  Such  a  surface  costs  not 
over  37  cents  per  square  yard  in  England,  and  from  ex- 
perience already  obtained,  it  is  believed  that  such  a  surface 
will  last  from  six  to  ten  years.  The  usual  method  employed 
in  England  in  this  construction  is  to  excavate  the  old  road 
surface  to  a  depth  of  about  3  inches  and  bring  the  new  surface 
up  to  the  old  grade  by  application  of  the  tarred  aggregate. 
The  cross-fall  of  such  a  road  need  not  exceed  1  in  50.  It  is 


116  HIGHWAY   ENGINEERING 

a  mistake  to  roll  the  layer  of  tarred  aggregate  with  a  roller 
weighing  over  11  tons.  It  is  advisable  to  apply  every  year 
or  every  alternate  year  a  light  coat  of  tar  to  such  a  surface 
in  order  to  ensure  waterproofing. 

Great  Britain.  ROBERT  DRUMMOND.  One  system  of 
constructing  a  tar  macadam  road  in  England  is  as  follows: 
the  method  of  application  is  similar  to  applying  an  ordinary 
coating  of  metal,  except  that  before  application  the  surface 
of  the  road  should  be  prepared  by  scarifying,  levelling  all 
inequalities  and  rolling  it  smooth.  The  tarred  stone  of  the 
required  thickness  is  then  applied  and  rolled  with  a  steam 
roller  and  bound  with  a  light  coating  of  tarred  chippings. 
Under  proper  conditions  this  method  makes  an  excellent 
roadway,  and  gives  it  a  very  much  longer  life  than  any  form 
of  approved  macadam  surface.  Taking  everything  into 
consideration  this  system  is  as  cheap  as  any  of  the  other 
systems,  and  gives  much  better  results.  It  is  only  the  ques- 
tion of  the  initial  expense  which  prevents  this  method  from 
being  more  generally  adopted.  The  additional  cost  of 
tarring  the  stone,  and  binding  it  with  tarred  chippings  is 
about  10  cents  per  superficial  yard. 

Italy.  PAOLO  CATTANEO.  The  method  of  construct- 
ing asphalt  pavements  in  Italy  is  as  follows:  on  a  concrete 
foundation,  laid  on  solid  ground  which  is  not  likely  to  settle, 
the  asphalt  is  spread  in  the  form  of  powder  heated  to  a 
temperature  of  100  degrees  Centigrade.  The  powder, 
which  is  obtained  from  the  pure  mineral,  must  be  homo- 
geneous and  free  from  any  foreign  substance.  It  must 
contain  at  least  10  per  cent  of  bitumen.  Next,  the 
thickness  of  the  soft  layer  must  be  reduced  from  3)4 
inches  to  2  inches  by  artificial  compression  by  means  of 
hot  tools.  The  smooth  surface  is  at  the  same  time 


BITUMINOUS   PAVEMENTS  117 

slightly  sprinkled  with  cement,  the  object  of  which  is  to 
fill  up  the  small  holes  on  the  surface.  The  street  can 
be  opened  for  traffic  in  twenty-four  hours  after  the  work 
is  finished.  j 

Switzerland.  VICTOR  WENNER  and  ARTHUR  SCHLAE- 
PFER.  Together  with  stone  paving,  asphalt  decidedly 
takes  the  first  place  among  hard  surfacings  in  Switzerland, 
rammed  asphalt  being  principally  employed  for  carriage- 
ways, and  asphalt  mastic  almost  exclusively  for  footways. 
The  foundation  always  consists  of  a  concrete  layer,  which 
in  carriageways  where  traffic  is  light  is  4  inches  thick, 
built  directly  on  a  well  drained  and  thoroughly  consolidated 
road.  For  heavier  traffic  the  concrete  has  a  stone  founda- 
tion of  6  inches  to  8  inches  in  depth.  With  rammed  asphalt 
the  gradient  of  the  road  may  reach  2  per  cent,  a  greater 
incline  rendering  the  pavement  too  dangerous  for  traffic  on 
account  of  slipperiness. 

Asphalt  plates,  12  inches  by  4  inches  by  2  inches,  made 
under  heavy  hydraulic  pressure,  are  also  used  to  some 
extent.  Diplolith  concrete  plates  10  inches  square  and  2 
inches  thick  are  laid  on  a  bed  of  lime  concrete,  and  on  these 
is  laid  a  J/2  incn  layer  of  asphalt  powder  applied  under 
heavy  hydraulic  pressure.  Both  of  these  types  of  pave- 
ment, however,  are  suitable  only  for  light  traffic. 

United  States.  ARTHUR  H.  BLANCHARD.  The  State 
Board  of  Public  Roads  of  Rhode  Island  built  its  first 
section  of  bituminous  macadam  pavement  in  1906.  The 
construction  of  this  section  consisted  of  placing  on  a  firmly 
compacted  subgrade  a  6  inch  layer  of  crushed  stone  vary- 
ing in  size  from  1%  inches  to  2J/2  inches.  After  this  course 
was  thoroughly  rolled  about  %  of  a  gallon  of  hot  coal 
tar  per  square  yard  was  spread  on  the  surface.  The  stone 


118  HIGHWAY   ENGINEERING 

for  the  surface  course,  varying  in  size  from  ^  of  an  inch 
to  1J4  inches,  was  next  deposited  on  a  mixing  platform 
and  thoroughly  mixed  with  hot  tar  by  using  rakes  and 
shovels  until  every  stone  was  completely  coated.  This 
mixture  was  laid  on  the  bottom  course  to  a  depth  of  3  inches 
and  rolled  to  2  inches.  Finally  a  thin  coat  of  ^  inch 
screenings  was  spread  on  this  surface  and  rolled.  The  tar 
used  was  a  crude  coal  tar  from  the  Providence  Gas  Com- 
pany. The  total  quantity  used  was  \%  gallons  per  square 
yard.  In  this  case  no  flush  coat  was  added,  since  motor 
vehicles  composed  90  per  cent  to  95  per  cent  of  the  total 
traffic.  When  inspected  in  October,  1909,  the  road  was  in 
as  good  condition  as  when  laid. 

In  1908  several  experimental  sections  were  laid,  one  by 
the  penetration  method,  the  rest  by  the  mixing  method  as 
constructed  in  1906,  except  that  in  some  cases  the  coating 
of  the  bottom  course  of  stone  with  tar  was  omitted.  The 
bituminous  materials  used  were  a  crude  coal  tar,  a  refined 
coal  tar,  a  mixture  of  crude  coal  tar  and  Texaco  asphalt 
Grade  H,  50  per  cent  of  each,  a  mixture  of  crude  coal  tar 
and  coal  tar  pitch,  75  per  cent  and  25  per  cent  of  each 
respectively,  and  Texaco  asphalt  grade  H.  The  stone  was 
mixed  by  hand  on  mixing  platforms.  Crude  coal  tar  was 
used  as  the  binder  for  the  stretch  built  by  the  penetration 
method.  This  binder  was  applied  by  means  of  dippers, 
1.87  gallons  per  square  yard  being  used.  In  the  case  of  the 
experiment  where  the  Texaco  asphalt  grade  H  was  used 
alone  as  the  binder,  mixed  with  cold  stone,  an  excessive 
amount  of  binder  was  necessary  in  order  to  partially  coat 
the  stone,  a  total  of  3.59  gallons  of  asphalt  being  used  per 
square  yard.  In  the  other  experiments  1J^  gallons  of  bi- 
tuminous material  were  used  per  square  yard.  The  cost  per 


BITUMINOUS    PAVEMENTS  119 

square  yard  in  excess  of  the  cost  of  ordinary  macadam 
construction  was  14.3  cents  for  the  experiment  built  by  the 
penetration  method,  40.1  cents  for  the  experiment  where 
asphalt  was  used  alone  as  the  binder,  and  from  12  to  15 
cents  for  the  other  experiments.  The  variation  in  cost 
depends  largely  upon  the  kind  and  amount  of  the  binder 
used. 

This  road  is  subjected  to  a  very  heavy  motor  car  traffic 
in  the  summer  months  and  a  very  limited  horse  drawn 
vehicle  traffic.  An  examination  of  the  sections  in  1909, 
after  they  had  been  used  two  summers  and  one  winter 
showed  that  very  good  results  had  been  obtained.  There 
was  no  apparent  difference  between  those  sections  in  which 
the  bottom  course  had  been  painted  and  those  in  which 
this  operation  was  omitted.  The  section  constructed  by 
the  penetration  method  showed  slight  disintegration  in 
spots,  due  probably  to  an  uneven  application  of  the  binder 
or  to  the  segregation  of  the  smaller  sizes  of  stone  in  the 
surface  course,  thus  preventing  sufficient  penetration  to  se- 
cure the  requisite  bond. 

One  section  built  in  1908  by  the  mixing  method  was 
constructed  with  a  crude  coal  tar  from  the  plant  of  the 
Attleboro  Gas  Gompany.  This  tar  was  not  as  good  as  that 
of  the  Providence  Gas  Company,  which  was  used  in  all 
other  cases.  Practically  all  of  the  1,000  feet,  in  which  the 
Attleboro  tar  was  used,  disintegrated  and  had  to  be  repaired 
before  the  end  of  the  season  by  painting  the  entire  surface 
with  about  one  gallon  per  square  yard  of  Texaco  asphalt. 
This  section  was  subjected  to  a  heavy  motor  car  traffic  and 
a  very  limited  horse  drawn  vehicle  traffic. 

One  section  of  2J4  miles  was  built  on  a  trunk  line  which 
is  subjected  to  both  excessive  motor  car  traffic  and  excessive 


120  HIGHWAY   ENGINEERING 

horse  drawn  vehicle  traffic,  there  being  about  50  per  cent  of 
each.  At  the  beginning  of  the  work  a  section  2,000  feet  in 
length  was  built  by  the  mixing  method,  Providence  coal 
gas  tar  being  used  as  the  binder.  Before  the  end  of  the 

1908  season  this  section  commenced  to  disintegrate  due  to 
the  impact  of  the  sharp  calks  of  horses'  hoofs  on  the  exposed 
stone  in  the  surface  course.     This  section  had  to  be  repaired 
early  in  1909  by  applying  a  flush  coat  of  tar  to  the  surface 
and  then  a  flush  coat  of  asphalt,  covered  with  a  layer  of 
chips.     The  remainder  of  the  2J4  miles  was  finished  with 
a  flush  coat  of  bituminous  material,  0.6  of  a  gallon  being 
used  per  square  yard,  in  order  to  provide  against  the  dis- 
integration caused  by  the  impact  of  the  horses'  feet.     The 
greater  part  of  the  road  was  built  by  the  mixing  method, 
using  in  the  mix  1)4  gallons  of  bituminous  material  con- 
sisting of  50  per  cent  of  Texaco  asphalt  grade  J  and  50 
per  cent  of  crude  coal  tar,  with  either  a  flush  coat  of  Texaco 
asphalt  grade  H  or  crude  tar.     With  the  approach  of  cold 
weather  crude  tar  was  used  alone  in  the  mix  and  Texaco 
asphalt  for  the  paint  coat.     In  the  latter  part  of  November, 
crude  tar  was  used  for  both  the  mix  and  the  paint  coat. 
During  1909,  these  various  sections  needed  only  slight  re- 
pairs and  in  October,  1909,  the  sections  which  had  been 
given  a  flush  coat  of  asphalt  were  almost  faultless.     The  cost 
of  these  sections  in  excess  of  the  cost  of  ordinary  macadam 
construction  varied  from  17  cents  to  about  21  cents  per 
square  yard. 

From  the  results  obtained  in  1908,  it  was  decided  in 

1909  to  adopt  as  the  standard  a  bituminous  pavement 
constructed  with  50  per  cent  of  Texaco  asphalt  and  50  per 
cent  of  Providence  tar  for  the  mix,  and  a  flush  coat  of  tar. 
Later  in  the  season  an  asphalt  flush  coat  was  substituted 


BITUMINOUS   PAVEMENTS  121 


for  the  tar.  From  1J4  to  2  gallons  of  material  per  square 
yard  were  used  in  mixing  the  stone,  while  the  amount 
used  for  the  flush  coat  varied  from  0.6  to  1  gallon  per 
square  yard. 

During  the  months  of  September  to  October,  1909, 
several  experimental  stretches  were  built  using  refined 
materials.  The  work  was  done  by  the  hand  mixing  method. 
In  each  experiment  the  surface  was  treated  with  a  flush 
coat  of  the  same  material  as  was  used  in  the  mix.  The 
bituminous  materials  used  were  a  refined  water  gas  tar, 
two  grades  of  refined  coal  tar,  two  grades  of  prepared 
mixtures  of  refined  coal  tar  and  asphalt,  and  a  so-called  85 
per  cent  asphaltic  binder.  In  connection  with  some  of 
these  experiments  the  tar  coating  machine  of  the  American 
Tar  Company  was  used. 

United  States.  WALTER  W.  CROSBY.  In  1909,  Park 
Heights  Avenue,  Baltimore,  was  treated  by  the  penetration 
method.  The  old  macadam  surface  was  scarified  to  a 
depth  of  2  inches  and  sufficient  new  stone,  varying  in  size 
from  1  to  2  inches  in  their  longest  dimensions,  was  added 
to  give  the  desired  crown.  The  stone  was  well  rolled  in 
order  to  reduce  the  voids.  It  was  estimated  that  twice 
the  ordinary  amount  of  rolling  was  done.  The  binder 
was  applied  hot  (80  degrees  to  150  degrees  Centigrade), 
and  in  most  cases  so  as  to  completely  fill  the  voids  in 
the  stone.  The  amount  of  material  used  varied  from 
5  gallons  to  1J^  gallons  per  square  yard.  Stone  chips 
were  spread  over  the  freshly  tarred  surface  to  a  depth 
of  from  J^  to  ^  of  an  inch  and  then  rolling  was  un- 
dertaken as  soon  as  convenient.  Later  any  excess 
binder  was  dusted  with  clean  sand.  Ten  different  ma- 
terials were  employed,  including  various  coal  tar  prep- 


122  HIGHWAY   ENGINEERING 

arations,  refined  water  gas  tar,  and  heavy  asphaltic  com- 
pounds.* 

It  is  too  soon  to  report  on  the  success  of  this  work 
but  a  narration  of  some  of  the  incidents  connected  with  it 
and  the  results  secured  to  date  may  be  of  interest. 

Material  number  one  was  an  asphaltic  compound.  It 
was  expected  to  use  about  2  gallons  of  binder  per  square 
yard  and  it  was  found  that  this  amount  was  just  about 
what  the  voids  of  the  rolled  stone  would  hold.  This 
material,  however,  had  a  tendency  to  rise  through  the  stone 
and  screenings.  Repeated  applications  of  sand  were  used 
on  these  places  with  the  result  that  in  some  instances  there 
now  exists  a  carpet  of  sand  and  bituminous  material  on  the 
road  to  a  depth  of  1^£  inches  over  the  stone.  Although 
this  carpet  did  not  pick  up,  it  was  noticed  that  the  resist- 
ance to  traction  was  greatly  increased,  especially  during 
the  warmer  hours  of  the  day.  These  effects,  apparently 
due  to  an  unnecessary  excess  of  the  binder,  gradually  de- 
creased with  age  and  are  at  present  (November,  1909) 
practically  unnoticeable  although  they  may  reappear  next 
summer.  The  use  of  1%  gallons  of  material  per  square 
yard,  instead  of  2  gallons  as  at  first,  considerably  reduced 
the  annoyances  above  described. 

Material  number  two  was  an  asphaltic  compound 
considerably  more  fluid  than  number  one,  which  made  it 
difficult  to  fill  the  voids  near  the  crown  of  the  road  without 
a  considerable  loss  of  material  at  the  sides.  On  account 
of  its  fluidity  3J/9  gallons  of  binder  per  square  yard  were 
used.  This  material  appeared  to  rise  to  the  surface  to  a 
slightly  greater  extent  than  number  one.  Otherwise  the 
results  seem  similar  to  those  obtained  with  material  number 

*  A  table  of  the  analyses  of  these  materials  is  given  on  page  70,  Chapter  V. 


BITUMINOUS   PAVEMENTS  123 

one,  except  material  number  two  does  not  set  as  quickly 
nor  as  much. 

Material  number  three  was  an  asphaltic  compound 
much  more  viscous  at  normal  temperatures  than  either 
number  one  or  number  two.  It  did  not  waste  at  the  sides 
as  did  those  others,  nor  did  it  give  nearly  as  much  trouble 
by  rising  to  the  surface.  It  set  much  more  readily  and  the 
usual  results  seemed  much  more  satisfactory.  About  3 
gallons  per  square  yard  were  used. 

Material  number  four  was  a  refined  water  gas  tar. 
Two  grades  were  used,  one  of  which  had  a  somewhat  lighter 
consistency  than  the  other.  Results  so  far  seem  similar 
to  those  where  material  number  three  was  used.  About 
3  gallons  were  used  per  square  yard. 

Material  number  five  was  supposed  to  be  a  refined 
coal  tar.  This  material  was  slightly  less  fluid  than  material 
number  four.  About  3J^  gallons  per  square  yard  were 
used. 

Material  number  six  was  a  refined  coal  tar  of  about  the 
same  consistency  as  material  number  two.  About  5 
gallons  per  square  yard  were  used. 

Material  number  seven  was  a  refined  water  gas  tar. 
Although  it  appeared  to  be  altogether  too  fluid  for  satis- 
factory use,  it  was  used  since  a  similar  material  had  been 
successfully  tried  out  in  1908.  Afterwards  it  was  found 
necessary  to  paint  all  but  about  1,000  square  yards  of  the 
work  with  the  lighter  grade  of  material  number  four.  In- 
vestigation showed  that  although  the  same  processes  for 
the  manufacture  had  been  followed  as  had  been  carried  out 
in  making  the  1908  tar,  a  change  in  the  character  of  the 
oil  used  by  the  gas  works  in  carburetting  the  gas  resulted 
in  a  totally  different  refined  tar  for  road  use.  Con- 


124  HIGHWAY   ENGINEERING 

sequently  the  further  use  of  this  particular  material  was 
abandoned. 

All  of  the  tars  with  the  exception  of  number  seven  gave 
results  that  so  far  seem  about  the  same  and  quite  similar 
to  those  where  material  number  three  was  used.  They 
were  more  adhesive  than  materials  numbers  one  and  two. 
They  set  quicker  and  do  not  give  nearly  as  much  trouble 
from  rising  to  the  surface  or  wasting  out  at  the  sides. 
Generally  speaking,  the  refined  coal  tars  were  the  easiest  to 
apply  as  they  reach  a  greater  fluidity  at  a  moderate  degree 
of  heat,  but  some  complaints  of  excessive  slipperiness  in 
cold  weather  have  been  received  on  the  section  where 
material  number  four  was  used. 

Material  number  eight  was  a  heavy  binding  oil,  in 
appearance  similar  to  number  two.  Its  action  and  results 
so  far  have  been  almost  identical  with  the  same  material. 
About  3^2  gallons  per  square  yard  were  used. 

Material  number  nine  was  a  refined  coal  tar  of  about 
the  same  consistency  as  material  number  five.  About  4 
gallons  per  square  yard  were  used. 

United  States.  HAROLD  PARKER.  An  experimental 
section  of  resurfacing  an  old  macadam  road  using  gravel 
and  an  asphaltic  oil  mixed  with  pure  bitumen,  or  an  oil 
with  a  very  large  percentage  of  asphalt,  was  constructed 
by  the  Commission.  The  road  so  constructed  was  pre- 
viously macadamized  in  1900,  and  was  badly  worn.  The 
surface  was  picked  up  by  a  steam  roller,  and  reshaped. 
The  rolling  of  this  reshaped  surface  was  not  very  severe, 
since  it  was  desired  to  have  the  stones  rather  loose  so  that 
the  crawling  of  the  top  coat  would  be  prevented.  The  oil 
and  asphalt  were  heated  separately  to  about  300  degrees 
to  400  degrees  Fahrenheit,  and  the  sand  to  about  225 


BITUMINOUS   PAVEMENTS  125 

degrees  Fahrenheit.  The  latter  was  thrown  on  thin  iron 
smoke  stacks  to  a  depth  of  about  1  foot  and  heated  by 
wood  fires.  The  mixing  was  done  by  hand,  first  on  wooden 
platforms,  and  later  on  steel  with  better  results.  After 
measuring  the  sand  and  gravel  by  means  of  a  measuring 
box,  about  one-third  of  the  required  quantity  of  hot  oil  was 
applied  in  small  quantities  and  the  mass  turned  over  once, 
next  the  full  amount  of  oil  was  added  and  the  mass  turned 
again,  finally  the  entire  amount  of  asphalt  was  added  and 
the  entire  mass  was  turned  until  thoroughly  coated.  The 
mixture  was  then  carted  to  the  road  and  was  either  shovelled 
directly  onto  the  ground  or  placed  on  dumping  boards,  the 
former  method  proving  the  better  since  there  was  less 
cooling  of  the  material.  After  a  careful  spreading,  the 
surface  was  rolled  gradually  as  the  material  cooled  and 
hardened.  Although  a  10  ton  roller  was  used,  the  writer 
believes  a  5  to  6  ton  tandem  roller  would  have  worked 
better. 

Seven  experiments  were  made.  About  18  gallons  of 
binder  were  used  per  cubic  yard  of  gravel.  In  two  experi- 
ments asphaltic  oil  was  used  as  the  binder  and  in  the  others 
varying  percentages  of  asphaltic  oil  and  pure  asphalt. 
Both  the  asphaltic  oil  and  the  oil  asphalt  were  required  to 
conform  to  specifications.  The  gravel  was  screened  to 
different  sizes  and  was  mixed  with  sand  that  would  pass 
through  a  J4  mcn  screen,  different  proportions  of  each  being 
used. 

To  obtain  perfect  results,  teaming  should  be  kept  off 
the  road  for  a  period  which  need  not  be  longer  than  twenty- 
four  hours  after  spreading. 

The  conclusions  reached  were  that  all  of  these  trials 
appear  to  be  successful;  that  where  the  traffic  is  heavy, 


126  HIGHWAY   ENGINEERING 

asphalt  should  be  added  proportionally.  For  ordinary 
use,  however,  asphalt  oil  without  the  addition  of  asphalt, 
mixed  thoroughly  with  gravel  composed  of  particles  not 
larger  than  would  pass  through  a  1/2  inch  screen,  will 
produce  a  road  that  will  withstand  the  wear  of  auto- 
mobiles and  other  traffic  in  a  satisfactory  and  economical 
manner. 

United  States.  JAMES  A.  W.  PINE.  The  writer 
believes  if  a  suitable  bituminous  cement  is  found,  that  the 
nearer  the  proportions  of  bituminous  cement,  sand  and 
stone  follow  the  present  practice  in  proportioning  hydraulic 
cement  concrete,  the  better  will  be  the  pavement.  If  hot 
liquid  asphalt  cement  is  used  it  should  be  first  mixed  with 
the  hot  sand  or  mineral  matter,  and  then  the  large  stone, 
heated  to  about  300  degrees  Fahrenheit,  should  be  added. 
Either  hand  or  machine  mixing  may  be  used. 

The  writer  condemns  the  penetration  method  since 
uniformity  cannot  be  obtained.  More  bituminous  cement 
is  required  for  this  method  and  it  cannot  be  distributed 
evenly.  Moreover  the  contraction  of  bituminous  concrete, 
after  having  been  put  in  place  while  hot  and  after  tamping 
or  rolling,  tends  to  make  the  resulting  pavement  more 
solid.  This  advantage,  of  course,  cannot  be  obtained  by 
the  penetration  method. 

A  method  suggested  for  using  Trinidad  asphalt  is  to 
pulverize  the  crude  asphalt  and  then  subject  the  granulated 
material  to  simple  evaporation  to  rid  it  of  water.  These 
operations  can  be  done  at  a  trifling  cost  and  the  product 
may  be  shipped  in  bulk  or  bags  for  delivery  direct  on  the 
work  where,  without  the  aid  of  any  special  melting  appara- 
tus, it  can  be  mixed  cold  with  the  previously  heated  mineral 
matter,  and  flux. 


BITUMINOUS   PAVEMENTS  127 

United  States.  JOHN  R.  RABLIN.  Some  of  the  roads 
of  the  Metropolitan  Parkway  system  have  been  constructed 
by  the  penetration  method.  The  bituminous  material  is 
applied,  at  a  temperature  from  150  degrees  to  200  degrees 
Fahrenheit,  to  the  top  course  of  stone  after  it  has  been 
thoroughly  rolled.  The  surface  is  then  rolled  again  after 
which  a  flush  coat  of  bituminous  material  is  applied  by 
brooms,  by  spraying,  or  by  some  other  form  of  distributing 
machine.  This  surface  is  covered  with  good  stone  screenings 
and  rolled.  Very  satisfactory  results  have  been  obtained  by 
this  method.  About  1J/2  gallons  of  refined  coal  tar  per 
square  yard  are  generally  used  for  the  first  application,  and 
a  mixture  of  refined  tar  and  residual  asphalt,  containing 
about  10  per  cent  of  asphalt,  is  used  for  the  flush  coat.  The 
object  of  the  asphalt  being  simply  to  prevent  the  tar  from 
becoming  brittle  and  hard  and  hence  slippery  under  traffic. 
The  writer  believes  that  the  use  of  a  clear  asphalt  is  ad- 
visable for  use  as  a  flush  coat  even  if  the  cost  is  increased. 

United  States.  GEORGE  C.  WARREN.  The  small 
investment  in  plant  necessary  and  the  very  cheap  method 
of  application  are  two  points  in  favor  of  the  penetration 
method.  The  disadvantages  of  this  method  are  the  in- 
sufficient coating  of  the  road  metal,  owing  to  the  inability 
of  the  bitumen  to  thoroughly  penetrate  small  voids;  the 
ravelling  of  the  road  if  the  bitumen  used  is  not  hard  or 
cementitious  enough;  the  poor  cohesive  results  attained  if 
the  voids  are  not  completely  filled  with  bituminous  material; 
the  consequent  oozing  of  the  material  to  the  surface  under 
traffic  in  hot  weather  if  sufficient  material  is  used  to  fill  the 
voids. 

Hand  mixing  is,  as  a  rule,  cheaper  than  machine  mixing 
because  there  is  no  expense  for  plant  installation  and  no  fuel 


128  HIGHWAY   ENGINEERING 

cost,  which  makes  it  especially  adapted  to  small  contracts. 
There  is  a  tendency  to  use  a  softer  bitumen  with  this  method 
in  order  to  secure  greater  ease  in  mixing.  The  less  accurate 
proportioning  and  distributing  of  materials  and  the  inability 
to  get  as  thorough  a  mix  are  also  disadvantages  of  this 
method. 

Mechanical  mixers  such  as  the  ordinary  concrete  mixer, 
either  of  the  continuous  or  batch  type,  may  be  used  without 
much  expense  if  the  ingredients  are  not  heated.  In  such  a 
case,  however,  the  disadvantage  of  using  a  bituminous 
material  so  soft  as  to  be  liquid  at  normal  temperature  is 
very  great.  Mixers  which  heat  but  do  not  proportion  the 
materials  are  better  but  still  defective. 

The  proper  mixing  machine  to  use  is  one  which  is 
specially  designed  to  heat  the  materials  and  which  will  give 
a  uniform  and  accurate  proportioning  of  both  bituminous 
material  and  stone.  It  should  have  heating  power  enough 
to  permit  the  use  of  a  bitumen  hard  enough  to  act  as  a 
true  binder.  It  should  produce  a  mixture  which,  when 
compressed  on  the  road,  will  be  dense  enough  to  prevent 
penetration  of  moisture  and  will  be  strong  enough  to  resist 
all  classes  of  traffic. 

The  writer  believes  that  the  necessary  essentials  to  the 
best  construction  are: 

1.  That  the  sizes  of  stone  or  mixture  of  stone  and  sand 
composing  the  mineral  aggregate  of  the  wearing  surface 
shall  be  scientifically  and  accurately  proportioned,  varying 
from  the  coarsest  size  permitted  by  the  thickness  of  the 
surface  (at  least  y%  of  an  inch  less  than  the  depth  of  com- 
pressed surface  desired),  down  to  an  impalpable  powder,  each 
size  so  proportioned  as  to  reduce  the  voids  to  the  greatest 
practicable  extent,  which  in  practical  work  can  be  as  low 


BITUMINOUS   PAVEMENTS  129 

as  10  per  cent  to  15  per  cent  of  the  volume.  To  practically 
produce  this  result  a  mixing  plant  designed  to  proportion 
and  control  the  sizes  of  the  aggregate  is  essential. 

2.  That  sufficient  bitumen  shall  be  used  to  thoroughly 
fill  the  remaining  voids  and  evenly  but  thoroughly  coat 
every  particle  of  aggregate,  large  and  small,  with  a  thin 
coating,  of  bituminous  cement.  By  using  a  bituminous 
material  of  the  proper  grade  and  with  thorough  com- 
pression, a  solid  construction  of  bituminous  concrete  is 
obtained.  This  concrete  is  within  5  per  cent  of  the  specific 
gravity  of  solid  rock  of  the  character  used  in  the  wearing 
surface.  This  difference  in  specific  gravity  represents  the 
difference  between  the  specific  gravity  of  the  stone  and  the 
bitumen  used  in  the  construction,  and  not  voids  or  lack  of 
density  or  stability  in  the  compressed  bituminous  concrete 
wearing  surface. 


CHAPTER  XII 

BRICK,   CONCRETE.   STONE  BLOCK  AND  WOOD   BLOCK 
PAVEMENTS 

BRADACZEK,  THEODOR,  Imperial  Commissioner  of  Public 
Works,  Prague,  Austria. 

BREDTSCHNEIDER,  AUGUST,  Commissioner  of  Public 
Works,  Charlottenburg,  Germany. 

DE  JAEGERE,  ALBERIC,  Civil  Engineer,  Antwerp,  Bel- 
gium. 

EISENLOHR,  Director,  Board  of  Public  Works,  Strasburg, 
Germany. 

FLECK,  GEORG,  Commissioner,  Board  of  Public  Works, 
Dresden,  Germany. 

FOCK,  EDOUARD,  Chief  Engineer,  Budapest,  Hungary. 

FROIDURE,  EUGENE,  Principal  Engineer  of  Bridges  and 
Roads,  Ypres,  Belgium. 

GLASNER,  ANTOINE,  Engineer,  Budapest,  Hungary. 

GUIET,  SAMUEL,  District  Inspector,  La  Roche-sur-Yon, 
France. 

HORBURGER,  Member,  Board  of  Public  Works,  Munich, 
Germany. 

LAFARGA,  PROSPERO,  Engineer  of  Highways,  Canals  and 
Harbors,  Alicante,  Spain. 

LE  GAVRIAN,  P.,  Engineer  of  Bridges  and  Roads,  Ver- 
sailles, France. 

MENCZER,  BELA,  Chief  Engineer,  Budapest,  Hungary. 

130 


BLOCK   ANI5   OTHER   PAVEMENTS  131 

SCHLAEPFER,  ARTHUR,  Street  Inspector,  Zurich,  Switzer- 
land. 

VAN  LOBEN  SELS,  M.  J.,  Vice-President,  Netherlands 
Association  of  Brick  Manufacturers,  Nimwegen,  Nether- 
lands. 

VERSTRAETE,  RICHARD,  Engineer  of  Bridges  and  Roads, 
Bruges,  Belgium. 

WENNER,  VICTOR,  City  Engineer,  Zurich,  Switzerland. 

Austria.  THEODOR  BRADACZEK.  The  localities  where 
pavements  are  employed  are  for  the  most  part  those  stretches 
of  the  Imperial  Roads  that  pass  through  the  towns  and  are 
maintained  by  the  communities. 

The  pavements  usually  consist  of  granite  cubes,  but 
in  many  places  they  are  made  of  the  round  topped  stones 
popularly  known  as  cobblestones.  The  replacement  of 
these  old  fashioned  cobblestones  with  cube  block  or  klein- 
pflaster  is  desired.  To  this  end  a  state  contribution  is  made 
to  the  communities  of  as  much  as  30  per  cent  of  the  cost 
of  a  strip  21  feet  in  breadth,  on  the  condition  that  they 
maintain  the  pavement  in  return.  In  places  where  there 
is  no  very  heavy  vehicle  traffic,  kleinpflaster  may  with 
advantage  be  applied  for  repaving.  The  old  paving  stones 
are  turned  up  on  end,  laid  deeper  to  act  as  a  foundation, 
and  rolled.  The  inequalities  are  remedied  by  a  layer  of 
concrete.  The  kleinpflaster  is  laid  over  this  layer  on  a 
thin  bed  of  sand  and  rammed  down. 

Belgium.  ALBERIC  DE  JAEGERE.  Stone  block  pave- 
ment:— The  paving  blocks  are  laid  with  the  longest  dimen- 
sions at  right  angles  to  the  direction  of  traffic,  the  usual 
foundations  consisting  of  a  sand  bed  4  inches  to  6  inches 


132  HIGHWAY   ENGINEERING 

thick.  At  Antwerp  where  the  traffic  is  intense,  a  ballast 
foundation  12  inches  thick  is  employed.  Upon  this  founda- 
tion is  spread  a  2  inch  bed  of  sand  to  serve  as  a  cushion 
layer  for  the  blocks.  Porphyry,  sandstone,  and  Swedish 
granite  are  the  materials  employed  for  making  the  stone 
blocks.  Porphyry  is  very  hard  and  long  lived  but  blocks 
made  of  it  become  slippery  with  wear,  while  sandstone  costs 
less  than  porphyry  but  wears  more  rapidly.  Swedish 
granite  blocks  are  very  satisfactory.  They  are  long  lived 
and  do  not  become  slippery. 

Wood  block: — Wood  pavement  blocks  usually  have 
about  the  following  dimensions:  thickness,  3J4  inches; 
width,  3  inches;  length,  8%  inches.  This  type  of  pavement 
is  laid  in  the  following  manner:  A  bedding  of  fine  cinders 
is  laid  4  inches  thick,  well  compacted  and  watered,  on  which 
is  spread  a  layer  of  macadam  6  inches  thick.  This  layer  of 
macadam  and  metal  is  watered,  compressed  and  rolled  so 
as  to  reduce  the  thickness  to  about  5  inches;  the  upper 
surface  is  dressed  to  the  final  camber  of  the  road  cross- 
section.  The  wood  blocks  are  first  dipped  for  fifteen 
minutes  in  a  bath  of  boiling  tar,  composed  of  heavy  oil  or 
creosote,  with  the  addition  of  l/&  part  of  tar,  and  then  laid 
in  a  bed  of  Rhine  sand  %  °f  an  incn  m  thickness  which  was 
previously  well  watered.  On  each  side  along  the  foot 
pavement  curb,  there  is  left  a  space  of  1J4  inches  in  width 
which  is  afterwards  filled  with  clay.  On  the  top  surface  a 
dressing  of  hot  tar  is  spread,  and  on  this  a  thin  layer  of  fine 
gravel.  Finally  this  latter  operation  is  periodically  renewed 
to  preserve  and  maintain  the  surface. 

Brick  pavement: — Another  system  of  paving  used  at 
Brussels  consists  of  a  pavement  of  tarred  bricks.  This 
pavement  has  been  laid  on  a  concrete  foundation  4  inches 


BLOCK  AND  OTHER  PAVEMENTS  133 

thick,  composed  of  a  mixture  of  0.92  cubic  yards  of  gravel 
and  551  pounds  of  cement.  The  bricks  are  the  kind  called 
"Straat  Klinkaert,"  and  are  submitted  to  a  preliminary 
heating  in  order  to  obtain  complete  dry  ness.  They  are 
then  plunged  for  three  hours  into  a  tar  boiler,  containing  a 
boiling  mixture  of  creosote  with  l/§  part  of  tar  added.  As 
in  the  case  of  wood  pavement,  the  surface  is  afterwards 
coated  with  tar  and  fine  gravel.  The  tar  has  the  effect  of 
making  the  bricks  more  elastic  and  more  resistant.  More- 
over, a  pavement  with  tarred  bricks  is  much  less  slippery 
than  wood  pavement. 

Concrete  pavement: — A  concrete  road  is  a  macadam 
in  which  the  binding  material  is  cement.  Unfortunately 
cement  wears  off  and  produces  a  disagreeable  dust.  The 
writer  is  of  the  opinion  that  slabs  constructed  of  various 
ingredients  mixed  with  cement  will  never  equal  natural 
materials  in  hardness  or  life. 

Belgium.  EUGENE  FROIDURE  and  RICHARD  VER- 
STRAETE.  In  1906  the  experiment  was  tried  of  brushing 
into  a  rolled  metal  surface  a  mortar  of  cement  and  sand. 
Rolling  was  also  carried  on  at  the  same  time  to  aid  in  the 
penetration  of  the  mortar.  The  results  were  satisfactory 
and  further  application  of  this  process  will  be  made.  An- 
other interesting  form  of  construction  tried  in  Belgium  is 
that  of  placing  between  two  layers  of  road  metal  a  layer  of 
slag  mortar.  Upon  rolling,  this  bed  of  mortar  penetrates 
into  both  layers.  These  roads  have  worn  well.  The 
mortar  which  is  considered  best  for  the  purpose  consists 
of  10  parts  of  fresh  granulated  slag,  2  parts  of  hydraulic 
lime  and  1  part  of  slow  setting  Portland  cement. 

France.  SAMUEL  GUIET.  The  writer  has  developed 
a  process  known  as  " Reinforced  Macadam"  which  consists 


134  HIGHWAY   ENGINEERING 

of  a  layer  of  cement  concrete  about  3  inches  thick  on  which 
is  placed  a  sheet  of  steel  wire^  or  expanded  metal.  This  is 
covered  by  a  layer  of  cement  mortar,  about  1%  inches  thick, 
in  which  is  placed  by  hand,  face  upward,  stone  metalling 
about  4  inches  in  size.  This  forms  a  monolithic  road- 
covering,  requiring  no  attention  and  is  exceedingly  durable. 

As  there  are  no  joints  in  this  pavement,  there  is  no 
shock  between  one  stone  and  the  next,  the  noise  being  con- 
sequently very  subdued  and  resembling  the  rolling  of  drums 
at  a  great  distance.  As  to  the  want  of  elasticity,  it  suffices 
to  say  that  since  the  advent  of  automobiles,  elasticity  is 
provided  for  in  the  wheel  tires,  and  in  the  spring  suspension 
of  the  chassis,  which  fact  justifies  the  construction  of  mono- 
lithic roads. 

Many  trials  with  this  form  of  pavement  in  places  where 
the  amount  of  traffic  makes  the  upkeep  of  macadam  im- 
practicable have  given  satisfactory  results.  The  pave- 
ment has  the  further  advantage  of  being  more  economical 
than  ordinary  paving,  and  no  more  costly  in  the  end  than 
macadam,  if  all  the  factors  which  go  to  make  up  a  road  be 
carefully  taken  into  consideration. 

France.  P.  LE  GAVRIAN.  The  method  usually  em- 
ployed in  the  construction  of  mortar  bound  macadam  roads 
is  to  mix  hydraulic  lime  with  sand,  spread  the  mixture  on 
the  road,  and  then  wash  it  in  by  sprinkling  with  water. 
The  process  is  not  to  be  recommended,  since  good  results, 
as  a  rule,  have  not  been  obtained.  The  extra  cost  above 
ordinary  metalling  is  about  5  cents  per  square  yard.  Cement 
has  been  used  hi  three  different  ways:  (1)  Mixed  with 
the  road  metal  and  spread  with  it  at  the  time  of  rolling. 
(2)  Spread  at  the  end  of  operations  either  neat  or  mixed 
with  sand,  either  as  mortar  or  mixed  dry  and  watered  after 


BLOCK  AND  OTHER  PAVEMENTS  135 

spreading.  (3)  As  mortar  mixed  with  the  road  metal. 
Cement  is  subject  to  the  same  faults  in  highway  con- 
struction as  is  lime,  there  being  a  similar  lack  of  elasticity 
as  shown  by  the  tendency  to  crack.  Slag  spread  over  well 
watered  broken  stone  has  given  very  fair  results. 

Germany.  AUGUST  BREDTSCHNEIDER;  HORBURGER; 
EISENLOHR;  and  GEORG  FLECK.  Stone  block  pavement : — 
The  material  used  for  stone  block  pavement  is  in  a  large 
measure  obtained  from  local  quarries  and  consists  princi- 
pally of  granite,  although  carbonated  sandstone,  graywacke, 
porphyry,  melaphyre,  greenstone,  diorite,  quartzite,  gabbro 
and  basalt  are  also  employed.  Of  the  stone  imported  from 
abroad  porphyry  from  Belgium  and  granite  from  Sweden 
are  important.  The  stones  employed  are  about  4  inches 
to  7  inches  in  breadth  and  from  about  5  inches  to  8  inches 
in  height  and  are  laid  with  the  long  dimension  perpendicular 
to  the  direction  of  the  roadway  or  in  some  cases  diagonal. 
The  bedding  consists  of  ballast,  although  concrete  laid  to 
a  thickness  of  8  inches  to  10  inches  is  sometimes  used. 
The  joint  filler  usually  consists  of  bitumen,  but  in  some  cases 
cement  mortar  is  employed. 

Artificial  stone  pavement  is  similar  to  that  with  square 
dressed  natural  stones.  This  type  consists  for  the  most 
part  of  blocks  whose  top  and  bottom  faces  are  about  6  inches 
square.  By  far  the  larger  part  of  the  blocks  are  made  of 
copper-schist  slag,  but  clinker  is  employed  in  very  small 
quantities.  The  stones  are  laid  in  exactly  the  same  manner 
as  are  the  natural  stone  blocks  used  in  square  dressed  pave- 
ment, partly  with  and  partly  without  joint  filling,  and 
without  solid  bedding.  The  town  of  Leipsic  has  a  compara- 
tively large  surface  of  carriageway  laid  with  copper-slag 
stones.  Clinker-stones  have  not  proved  satisfactory. 


136  HIGHWAY   ENGINEERING 

Kleinpflaster  has  come  into  vogue  within  the  last 
decade.  It  consists  of  polygonally  dressed  stones  of  from 
2J^  inches  to  4  inches  square,  mostly  of  hard  stone  such  as 
granite  and  basalt,  but  also  of  graywacke,  porphyry  and 
greenstone.  It  is  used  as  an  improvement  over  macadam, 
being  laid  in  coarse  sand  after  the  removal  of  the  upper 
parts  of  the  ballast  layer.  It  is  in  many  towns  coming  more 
and  more  into  favor.  In  Brunswick  it  covers  a  surface  of 
239,200  square  yards. 

Wood  block  pavement: — Wood  block  pavement  has 
not  been  introduced  into  Germany  to  the  extent  which  it 
has  in  France  and  England.  The  usual  method  of  laying 
the  pavement  in  Germany  is  to  place  the  blocks  directly 
on  a  concrete  base  10  inches  thick  and  fill  the  joints  with 
cement  grout  or  bitumen  according  as  the  wood  is  soft  or 
hard  respectively. 

Concrete  pavement: — Concrete  pavement,  such  as  the 
so-called  Kieserling  pavement,  is  intended  to  give  a  jointless 
surface  like  that  made  of  asphalt.  This  pavement  consists  of 
a  basalt  stone  concrete.  It  is  laid  to  a  thickness  of  2  inches 
to  2%  inches  on  the  concrete  foundation  layer  while  the  latter 
is  still  soft.  It  is  provided  with  expansion  joints.  Kieserling 
pavement  has  been  introduced  into  a  number  of  towns. 

Hungary.  ANTOINE  GLASNER.  The  paved  road  is 
constructed  in  Hungary  in  two  ways,  as  large  standard 
pavement  and  as  small  standard  pavement.  A  firm  founda- 
tion is  not  so  essential  in  the  case  of  the  large  standard 
pavement  as  it  is  for  the  small  standard  pavement.  In  the 
former  the  stones  are  of  such  a  size  that  they  are  not  easily 
displaced,  but  in  the  latter  form  of  pavement  the  traffic 
will  quickly  ruin  the  surface  if  the  stones  are  not  placed  on 
a  firm  foundation. 


BLOCK  AND  OTHER  PAVEMENTS  137 

In  Hungary  small  standard  pavement  is  usually  placed 
at  an  angle  of  45  degrees  with  the  axis  of  the  road.  The 
roadway  is  first  carefully  shaped  and  rolled,  and  then  the 
stones  are  placed  on  this  surface  as  compactly  as  possible, 
after  which  the  joints  are  filled  with  wet  sharp  sand.  The 
road  is  then  rolled  with  a  steam  roller  until  the  stones 
cease  to  yield  to  the  pressure.  A  thin  layer  of  sand  is 
then  added.  The  stones  used  are  about  3  inch  to  4  inch 
cubes,  usually  having  very  regular  surfaces.  These  pave- 
ments are  elastic,  easy  under  traffic,  clean  and  practically 
impermeable  to  water,  and  are  suitable  even  under  fairly 
heavy  traffic  in  towns.  They  also  make  a  good  foundation 
for  a  future  stronger  pavement. 

Hungary.  EDOUARD  FOCK  and  BELA  MENCZER.  Stone 
block  pavement: — Stone  block  pavement  is  laid  as  follows 
in  Hungary:  Blocks  of  three  sizes  are  in  general  use,  the 
full  sized  blocks  measuring  7  inches  by  7  inches  by  7  inches, 
the  three-quarter  sized  blocks  measuring  7  inches  by  7  inches 
by  5  inches,  and  conical  shaped  blocks  measuring  7  inches 
square  on  the  top  face  and  having  a  bottom  face  of  two- 
thirds  the  area  of  the  top  face.  The  customary  foundation 
is  composed  of  well  rolled  metalling.  Concrete  is  not 
frequently  used  because  it  causes  the  road  to  lose  its  elas- 
ticity and  also  makes  excavating  for  underground  pipes, 
etc.,  a  difficult  proposition.  The  blocks  are  laid  with  their 
edges  diagonal  to  the  direction  of  traffic,  experience  having 
shown  that  the  wear  is  less  with  this  arrangement  than  with 
the  method  of  laying  them  square  with  the  direction  of  the 
road.  The  practice  of  pouring  cement  mortar  into  the 
interstices  is  not  to  be  recommended.  Filling  the  joints 
with  clean  sand  has  given  satisfaction. 

Wood  block  pavement: — The  use  of  wood  is  limited 


138  HIGHWAY   ENGINEERING 

to  the  Capital,  since  the  unfavorable  results  there  obtained 
with  this  material  do  not  encourage  the  provincial  towns 
to  adopt  it.  Hitherto  pine  and  fir  wood  blocks  have  been 
used  for  wooden  pavements.  An  experimental  pavement 
with  larch  blocks  has  not  yet  been  long  enough  in  use  to 
enable  a  definite  opinion  to  be  formed  concerning  it. 

Netherlands.  M.  J.  VAN  LOBEN  SELS.  Nearly  two- 
thirds  of  the  State  Roads  are  constructed  of  brick  with 
dimensions  approximately  2  inches  by  4  inches  by  8  inches. 
In  South  Holland  there  are  made  bricks  called  "Rijnorm 
(Rhine  Bricks)"  which  are  smaller,  and  measure  1%  inches 
by  3^  inches  by  7  inches,  as  well  as  those  of  "  Utrecht," 
which  have  the  same  dimensions  as  the  "Rijnorm."  These 
small  bricks  form  excellent  road  surfaces,  free  from  dust 
and  mud,  proving  satisfactory  in  summer  and  in  winter. 
The  small  bricks,  " Rijnorm"  and  "Utrecht,"  are  excellent 
for  foot  pavements. 

In  order  that  a  brick  paved  road  may  be  well  made,  it 
is  first  necessary  to  thoroughly  roll  the  bed,  as  is  the  case  in 
all  other  roads.  This  foundation  is  then  covered  with  a 
layer  of  sand.  The  bed  of  sand  having  been  completed, 
the  bricks,  taken  one  at  a  time,  are  laid  as  close  as  possible 
against  each  other  in  lines  at  right  angles  to  the  axis  of  the 
road  and  struck  lightly  with  a  paving  mallet.  Each  con- 
secutive line  bonds  the  next  by  half  a  brick,  or  the  bricks 
are  laid  in  herring  bone  fashion.  The  brick  roadway  is 
curbed  by  a  few  longitudinal  rows  which  form  the  gutter. 
After  laying,  the  bricks  are  forced  into  the  sand  beds  by 
means  of  tampers,  and  the  joints  are  filled  with  sand  by 
means  of  brooms.  The  whole  road  surface  is  covered 
for  some  time  with  a  bed  of  sand  about  %  of  an  inch 
thick. 


BLOCK  AND  OTHER  PAVEMENTS  139 

The  following  advantages  are  claimed  for  a  brick  pave- 
ment: 

1.  The  maintenance  is  simple.     A  roadman   of   slight 
intelligence  can,  provided  that  constructional  work  is  iiot 
expected  of  him.  render  satisfactory  services. 

2.  A  roadway  is  obtained  which  will  usually  have  little 
dust  in  summer  and  little  mud  in  winter. 

3.  Partial  uncovering  for  repairing  the  foundation  can 
be  easily  made. 

Spain.  PROSPERO  LAFARGA.  The  porphyry  used  for 
stone  block  pavements  is  dark  grey,  very  hard,  tough,  dense, 
waterproof  and  exceedingly  difficult  to  work.  The  blocks 
of  porphyry  employed  in  Spain  are  roughly  rectangular 
parallelopipedons,  and  are  generally  from  7  inches  to  9^ 
inches  long,  4  inches  to  5  inches  wide,  and  5  inches  to  6 
inches  deep.  The  upper  face  should  be  practically  flat, 
but  the  other  faces  may  be  in  a  rougher  state,  provided  the 
width  of  joints  does  not  exceed  one  inch.  Porphyry  blocks 
are  laid  on  a  sand  foundation  at  right  angles  to  the  line  of 
the  gutter.  The  side  slope  of  the  pavement  should  be  slight, 
one  of  1  in  200  allowing  the  water  to  run  freely  to  the 
gutters.  The  cost  of  this  type  of  paving  varies  from  $2.67 
to  $5.44  per  square  yard. 

Switzerland.  VICTOR  WENNER  and  ARTHUR  SCHLAE- 
PFER.  Stone  block  pavement: — The  roads  in  the  interior 
of  the  Swiss  towns  have,  since  the  olden  days,  been  paved 
with  cobbles.  The  introduction  of  water-supply  and  other 
pipe  systems  at  the  end  of  the  last  century,  necessitating 
the  excavation  of  the  roads,  brought  about  the  substitution 
of  a  new  and  more  rationally  constructed  pavement  in 
place  of  the  old  cobblestone  surface. 

The   stone   pavement   of   the   carriageway   is   almost 


140  HIGHWAY   ENGINEERING 

without  exception  laid  in  sand  either  with  or  without  a 
substratum  of  stone,  upon  a  well  rammed  or  rolled  founda- 
tion. When  the  sublayer  is  thoroughly  drained  and  firm, 
that  is,  when  the  paving  is  to  be  laid  down  upon  an  already 
existing  road  or  upon  a  firm  stone  foundation,  the  bed  of 
stone  is  left  out  and  the  layer  of  sand  is  made  6  inches  to 
10  inches  thick.  In  the  construction  of  new  roads  the  bed 
of  stone  is  6  inches  to  8  inches  thick,  upon  which  a  layer  of 
sand  and  gravel  of  4  inches  to  6  inches  is  placed  as  the  bear- 
ing foundation. 

Wood  block  pavements: — The  employment  of  wooden 
pavements  has,  up  to  the  present,  been  comparatively 
small  in  Swiss  towns,  because  on  the  one  hand  cheap,  soft 
wood  pavements  are  not  sufficiently  durable  for  our  climatic 
conditions  and  on  the  other  hand  the  hard  wood  pavements 
are  too  expensive.  In  addition  to  this  the  jointed  layer  of 
the  wooden  pavement  has  hygienic  disadvantages  in  com- 
parison with  a  jointless  layer  like  that  of  asphalt.  This 
is  particularly  the  case  with  soft  wood,  in  consequence  of 
its  greater  capacity  for  the  absorption  of  water  and  refuse. 
These  defects  can,  to  a  certain  extent,  be  effectually  met  by 
the  regular  tarring  of  the  surface,  which  at  the  same  time 
renders  the  soft  wood  layer  more  durable. 

Brick  pavement: — "Ceramite"  or  "Rustolith"  pave- 
ment has  been  employed  to  some  extent  and  is  considered 
satisfactory  even  under  heavy  traffic.  It  consists  of  hard 
burnt  tiles  8  inches  by  4  inches  by  3  inches,  and  is  laid  on  a 
layer  of  concrete  with  a  bed  of  cement  mortar  or  sand.  A 
final  coating  of  liquid  cement  mortar  covers  the  whole  and 
entirely  fills  all  joints. 


CHAPTER  XIII 

TRACKWAYS 

DE  MORLOT,  ALBERT,  Chief  State  Inspector  of  Public 
Works,  Bern,  Switzerland. 

LE  GAVRIAN,  P.,  Engineer  of  Bridges  and  Roads,  Ver- 
sailles, France. 

NESSENIUS,  ADOLF,  Commissioner  of  Public  Works, 
Province  of  Hanover,  Germany. 

SANCHIS,  VINCENT,  Engineer  of  Highways,  Canals  and 
Harbors,  Valencia,  Spain. 

France.  P.  LE  GAVRIAN.  Inquiries  have  revealed 
that  only  the  Griende  Department  has  employed  trackways 
in  paved  roads.  Experiments  with  two  metalled  trackways 
on  a  paved  surface,  with  two  paved  trackways  on  a  metalled 
surface,  and  with  channel  irons  placed  longitudinally,  have 
been  carried  out  by  this  department.  According  to  the 
report  of  the  chief  engineer  the  results  have  not  been  suc- 
cessful. 

Germany.  ADOLF  NESSENIUS.  Iron  trackways  have 
been  constructed  with  very  satisfactory  results  in  different 
provinces  since  1894.  In  the  Province  of  Hanover  alone, 
on  April  1st,  1910,  there  were  about  28  miles  of  trackways 
in  use  and  4  miles  under  construction. 

Spain.  VINCENT  SANCHIS.  Climatic  conditions  in 
Valencia  are  very  unfavorable  for  metalled  roads.  Hard 

141 


142  HIGHWAY   ENGINEERING 

stone  suitable  for  paving  is  not  found  close  by  and  con- 
sequently is  very  expensive.  For  these  reasons  a  metal 
trackway  for  ordinary  vehicles  was  constructed  in  1892, 
which  has  been  in  constant  use  ever  since.  This  was  a 
double  trackway,  each  rail  being  constructed  of  two  bars  of 
inverted  U-shape  fastened  together  by  bolts  and  jointed 
together  end  to  end  by  fish  plates.  The  weight  of  rails 
is  152  pounds  per  yard.  The  gauge  of  the  tracks  was 
maintained  by  flat  tie  bars.  The  gauge  of  each  track 
was  the  same  as  the  gauge  of  horse  drawn  vehicles.  The 
tracks  were  sunk  2  inches  below  the  level  of  the  paving,  and 
consequently  vehicles  experienced  some  difficulty  in  leaving 
the  track.  Rutting  beside  each  rail  developed  from  this 
condition.  Traffic  over  these  metal  trackways  is  conducted 
with  great  order  and  regularity.  Loaded  vehicles  take  to 
the  track  one  after  the  other,  both  coming  and  going. 
Empty  vehicles,  passenger  carriages  and  automobiles 
keep  to  the  middle  of  the  road,  clear  of  the  rails,  and  can  go 
very  fast  without  causing  the  annoyances  so  usual  on  busy 
roads,  where  vehicles  pursue  erratic  courses  which  interfere 
with  the  general  traffic  and  are  at  times  a  source  of  real 
danger.  Where  the  loaded  traffic  is  all  in  one  direction  the 
writer  is  of  the  opinion  that  a  single  track  is  sufficient.  The 
maintenance  cost  for  a  metal  trackway  is  very  slight  and 
traction  is  very  easy.  The  wear  on  the  track  built  in  1892 
has  been  0.0039  inches  per  year. 

Switzerland.  ALBERT  DE  MORLOT.  Granite  track- 
ways have  been  constructed  in  several  different  cities  of 
Switzerland.  These  trackways  are  each  about  2  feet  wide, 
about  1  foot  thick,  and  are  spaced  about  4  feet  apart  on 
centers.  The  pavement  which  surrounds  them  is  of  a 
different  character  and  smaller  dimensions.  The  easy 


TRACKWAYS  143 

running  of  the  vehicles,  the  proximity  of  suitable  materials 
with  which  to  build  the  trackways  and  the  small  expense 
for  maintenance  justify  the  use  of  trackways.  The  track- 
ways become  slippery  in  time  and  in  consequence  have  to  be 
roughened. 


CHAPTER  XIV 

FOOTWAYS  IN  TOWNS  AND  CITIES 

HENDRICKS,  C.  J.,  Manufacturer  of  Paving  'Bricks, 
Woerden,  Netherlands. 

LE  Roux,  NICOLAS,  Engineer  of  Bridges  and  Roads, 
Angers,  France. 

MELLO  DE  MATTOS,  JOSE,  Engineer,  Lisbon,  Portugal. 
ROLDAN  Y  PEGO,  MANUEL,  Engineer,  Lisbon,  Portugal. 

TRUSLER,  GEORGE  D.,  A.  M.,  C.  E.,  Civil  Engineer, 
London,  England,  Great  Britain. 

France.  NICOLAS  LE  Roux.  The  width  for  footways 
in  France  is  generally  made  one-fifth  of  the  total  width  of 
streets  between  property  lines.  For  a  33  foot  street  the 
width  of  footway  can  be  about  6J^  feet.  On  streets  of  less 
width  than  33  feet  the  proportion  of  one-fifth  might  be 
reduced  somewhat,  whereas  on  streets  of  a  width  greater 
than  about  65  feet  the  proportion  might  well  be  increased 
to  at  least  one-quarter.  In  very  remote  streets,  if  there  is  a 
possibility  of  providing  for  two  vehicles  to  pass  each  other, 
this  should  be  accomplished  even  if  the  footways  have  to  be 
entirely  sacrificed.  If,  on  the  other  hand,  the  width  of 
roadway  is  only  sufficient  for  one  vehicle  to  pass,  the  foot- 
ways should  occupy  all  of  the  width  over  and  above  that 
necessary  for  the  passage  of  one  vehicle. 

The  transverse  slope  of  the  footway  depends  upon  the 
width  and  kind  of  surface.  It  should  be  sufficient  for  the 

144 


FOOTWAYS   IN   TOWNS  AND   CITIES  145 

easy  running  off  of  the  water,  but  not  great  enough  to  cause 
inconvenience  to  the  pedestrians.  In  France  the  transverse 
slope  is  generally  between  1  in  50  and  1  in  20,  the  smaller 
slope  being  used  when  the  surface  is  some  form  of  smooth 
paving.  The  different  materials  used  for  constructing  the 
surfaces  of  the  footways  are  asphalt,  tile  or  brick  paving, 
cement  paving,  granite  paving  and  paving  with  small 
stones. 

The  construction  of  footways  with  asphalt  is  as  follows : 
Natural  asphalt  is  mixed  with  sand  and  laid  to  a  thickness 
of  about  1  inch  on  a  cement  concrete  base  about  4  inches 
thick,  the  top  of  which  has  been  treated  with  a  layer  of 
cement  mortar  y%  of  an  inch  to  1  inch  in  thickness.  A  thin 
layer  of  gravel  is  spread  on  the  surface  and  gently  rammed  in 
while  the  asphalt  is  still  warm. 

The  advantage  of  a  tile  paving  is  that  it  may  be  made 
ornamental.  It  is  more  costly  than  asphalt,  but  it  may 
easily  last  25  years,  provided  it  is  made  of  good  material. 
The  usual  size  of  tiles  is  5  inches  to  5J^  inches  square  and 
1J4  inches  to  1J/2  inches  thick.  They  are  usually  embedded 
in  mortar  but  occasionally  only  in  sand.  The  joints  are 
filled  with  cement  by  flushing  the  surface  with  rich  mortar. 

Cement  paving  presents  a  better  appearance  than  does 
asphalt,  costs  less  as  a  rule,  and  the  hardness  of  its  surface 
is  generally  sufficient  to  make  it  last  a  good  while.  This 
type  of  pavement  consists  of  a  layer  of  cement  concrete 
about  3J^  inches  to  5  inches  thick  laid  on  a  carefully  prepared 
sand  foundation.  The  concrete  is  covered  with  a  coating 
of  rich  sand  mortar  %  of  an  inch  to  1J4  inches  thick.  The 
surface  of  this  coating  is  roughened  with  a  roller  and  marked 
with  grooves,  giving  it  the  appearance  of  a  slab  pavement. 
In  spite  of  every  care  taken  in  the  construction,  and  in  the 


146  HIGHWAY   ENGINEERING 

choice  of  materials,  it  is  very  seldom  that  the  paving  does 
not  show  hair  cracks  which  are  not  easy  to  repair.  Cement 
paving  is  extensively  used  for  footways  in  some  towns 
where  the  materials  composing  it  are  easily  procured. 

The  finest  footways  in  Paris  are  formed  of  granite 
slabs,  which  may  be  said  to  last  an  indefinite  time.  The 
cost  of  this  pavement  varies,  but  is  always  rather  high. 
The  slabs  are  about  6  inches  thick  and  are  bedded  in  con- 
crete. The  surface  is  tooth  axed,  but  wears  smooth  in  time, 
although  very  slowly.  -This  style  of  pavement  is  only 
suitable  for  footways  on  central  streets  with  slight  grades 
which  carry  a  heavy  foot  traffic. 

Stone  paving  has  doubtless  been  in  use  from  time 
immemorial.  Footways  have  generally  been  paved  with 
stones  obtained  from  the  cutting  down  of  old  stone  blocks. 
These  will  all  become  very  slippery  and  rounded  so  that 
walking  over  them  is  very  troublesome.  This  kind  of 
paving  should  not  be  allowed  except  in  footways  away  from 
the  center  of  towns  where  they  are  subjected  to  hard  usage 
and  where  they  are  often  used  for  the  unloading  or  stacking 
of  heavy  goods. 

The  footways  must  be  protected  on  the  carriageway 
side  by  a  solid  curb.  Too  often  the  curb  is  made  up  of  a 
row  of  headers  or  even  of  stone  blocks  bedded  in  sand  and 
hardly  let  into  the  roadway  at  all.  Such  curbs  should  not 
be  allowed.  On  important  streets  the  curb  should  invariably 
be  made  up  of  dressed  stone.  The  upper  face  of  the  curb- 
stone should  be  dressed  in  accordance  with  the  transverse 
slope  of  the  footway.  The  front  face  where  visible  should 
have  a  sufficient  batter  to  keep  the  vehicles  from  touching 
the  top  edge  of  the  curb. 

Trees  can  only  be  placed  on  footways  which  are  so 


FOOTWAYS   IN    TOWNS   AND    CITIES  147 

wide  that  they  do  not  cause  inconvenience  either  to  the 
traffic  or  to  residents  on  the  streets.  They  should  be  placed 
far  enough  away  from  the  edge  of  the  curb  so  that  they  may 
escape  being  hit  by  projections  from  vehicles  and  also  so 
that  the  roots  will  not  displace  the  curb.  They  should 
also  be  far  enough  from  the  houses  so  that  the  branches  will 
not  inconvenience  the  inhabitants  either  by  depriving  them 
of  light  or  by  injuring  the  walls  or  the  roofs  of  their  houses. 
Trees  should  therefore  only  be  placed  on  footways  at  least 
13  feet  wide.  Where  trees  are  planted  on  paved  footways 
an  open  space  should  be  left  around  each  tree,  not  only  in 
the  interest  of  the  tree  but  to  prevent  its  disturbing  the 
pavement  during  its  growth. 

Great  Britain.  GEORGE  D.  TRUSLER.  Under  the 
London  Building  Act  a  common  width  of  roadway  of  40 
feet  is  required,  which  provides  for  a  carriageway  24  or  25 
feet  wide,  the  remaining  16  or  15  feet  being  divided  up 
equally  on  each  side  of  the  carriageway  for  the  footways. 

In  the  case  of  natural  and  artificial  flagstone  footways 
it  is  customary  to  bed  the  flagstone  in  lime  mortar  on  a 
layer  of  clinkers  2  or  3  inches  in  thickness.  Footways 
having  a  surface  of  this  kind  are  built  with  a  cross-fall  of 
1  in  30  to  40.  The  writer  believes  that  Yorkstone  is  very 
superior  to  any  other  form  of  flag  paving.  It  wears  well  and 
gives  satisfaction.  It  is  extensively  used  by  the  London 
County  Council  on  street  widenings  and  improvements  and 
is  found  to  be  more  satisfactory  than  any  other  form  of 
paving. 

The  most  favored  form  of  in  situ  paving  for  footways 
in  the  City  of  London  is  asphalt.  It  is  found  to  be  practi- 
cally non-slippery,  wears  even  and  is  easily  patched.  The 
natural  rock  powder  compressed  is  used  and  is  preferred  to 


148  HIGHWAY  ENGINEERING 

the  mastic  where  there  is  a  continuous  traffic,  since  it  is 
tougher  and  wears  very  much  longer,  but  if  laid  in  sections 
not  much  used  it  wears  rough  and  crumbles.  In  the  main 
thoroughfares  of  the  city  the  asphalt  is  laid  on  a  3  inch 
concrete  foundation  to  a  thickness  of  1J^  inches  when 
compressed.  It  will  wear  from  four  to  five  years  without 
requiring  patching  and  repairs.  Asphalt  is  usually  laid 
with  a  fall  of  from  1  in  40  to  50.  The  footways  are  flushed 
with  water  at  night  and  squeegeed  leaving  them  perfectly 
clean  and  sanitary. 

Netherlands.  C.  J.  HENDRICKS.  In  Holland  the  foot- 
ways are  constructed  with  widths  varying  from  6.4  feet  to 
12.8  feet  according  to  the  intensity  of  the  traffic. 

Footways  having  surfaces  of  asphalt,  cement,  or  other 
materials  set  in  cement  have  certain  disadvantages,  since 
they  are  apt  to  become  slippery  during  rains,  may  crack 
in  winter  and  make  an  impermeable  covering  over  the  sub- 
soil. If  the  roadway  is  laid  with  a  covering  which  is  im- 
permeable to  water  and  air  it  is  better  to  place  the  water 
pipes,  gas  pipes,  etc.,  under  the  foot  pavements  where  they 
can  be  easily  accessible.  Again  there  is  danger  that  gas 
may  perhaps  arise  from  the  subsoil  and  find  its  way  out 
through  adjoining  houses  if  the  footway  is  covered  with 
impermeable  materials.  This  latter  disadvantage  of  im- 
permeable coverings  is  of  great  importance  in  Holland, 
which  lies  for  a  great  part  on  a  morass  foundation.  It  is 
a  consideration  of  the  above  features  and  the  low  cost 
which  has  given  rise  in  Holland  to  the  general  acceptance 
of  brick  as  the  best  suited  material  for  the  paving  of  streets 
and  footways. 

The  Rhine  brick,  made  from  clay  deposits  near  the 
Rhine,  is  particularly  suited  for  footways.  The  bricks  are 


FOOTWAYS   IN   TOWNS   AND    CITIES  149 

about  7  inches  by  3J/2  inches  by  2  inches  in  size  and  are  gen- 
erally bluish  in  color  on  the  outside  and  bluish  red  on  the 
inside.  Its  very  good  appearance,  low  cost,  retention  of 
its  rough  surface  even  under  wear,  and  easy  removal  are 
some  of  the  advantages  claimed  for  a  pavement  laid  with 
this  kind  of  brick.  The  bricks  are  laid  on  a  well  rammed 
sand  or  gravel  bed,  and  the  joints  are  then  filled  with  sand. 
Footways  constructed  with  Rhine  bricks,  laid  more  than  25 
years  ago,  can  be  found  in  several  of  the  cities  in  Holland. 
Portugal.  MANUEL  ROLDAN  Y  PEGO,  and  JOSE  MELLO 
DE  MATTOS.  A  system  for  foot  pavements  is  used  in 
Lisbon  and  other  Portuguese  towns  which  consists  in  laying 
at  random  small  stone  blocks  in  arcs  of  circles,  with  close 
joints,  on  a  properly  prepared  foundation.  A  hard  lime- 
stone and  a  basalt  are  used  for  this  work  and  by  means  of 
templets  the  workmen  are  enabled  to  lay  the  stone  in  fancy 
designs,  which  together  with  the  contrast  brought  out  by 
the  two  colors  of  stone  make  a  very  pleasing  effect  to  the 
eye.  It  is  claimed  that  the  rain  water  runs  off  footways 
built  of  this  material  without  any  appreciable  soaking  into 
the  subsoil.  In  addition  to  their  artistic  appearance  these 
sets  wear  very  slowly  and  evenly,  notwithstanding  the  great 
difference  in  quality  of  the  two  materials  employed. 


CHAPTER  XV 

ROAD   MACHINERY  AND  TOOLS 

BLANCHARD,  ARTHUR  H.,  M.  Am.  Soc.  C.  E.,  Deputy 
Engineer,  Rhode  Island  Stale  Board  of  Public  Roads,  Provi- 
dence, R.  L,  U.  S.  A. 

GOLA,  EMILIO,  Engineer,  Milan,  Italy. 

MACHNCTSCH,  RUDOLF,  Imperial  Chief  Engineer,  Gorz, 
Austria. 

PELLE,  C.  F.  J.,  Engineer  of  Bridges  and  Roads,  Paris, 
France. 

PONS,  ALFRED,  District  Inspector,  Montpellier,  France. 
THOMAS,  EDMOND,  Civil  Engineer,  Brussels,  Belgium. 

VERGER,  CASIMIR,  Assistant  Engineer  of  Bridges  and 
Roads,  Paris,  France. 

WAICHT,  CESLAV,  Engineer  of  Highways,  Warsaw, 
Russia. 

WAKELAM,  H.  T.,  M.  Inst.  C.  E.,  County  Engineer  of 
Middlesex,  Westminster,  London,  England,  Great  Britain. 

Austria.  RUDOLF  MACHNITSCH.  On  account  of  the 
steep  gradients  encountered  on  the  mountain  roads  of 
southern  Austria  compression  is  obtained  either  by  rolling 
with  a  hand  roller  or  by  diverting  the  traffic  to  the  newly 
constructed  road.  The  light  roller  mentioned  is  made  of 
concrete  and  weighs  882  pounds.  One  of  these  is  provided 

150 


ROAD   MACHINERY   AND   TOOLS  151 

for  each  twelve  miles  of  road.  Each  road  attendant  is  also 
provided  with  a  variety  of  small  hand  tools,  such  as  crow- 
bars, drills,  hammers,  picks,  shovels,  rakes,  straight-edge, 
water-level,  etc. 

Belgium.  EDMOND  THOMAS.  Among  the  advantages 
of  the  petrol  driven  roller  over  the  old  types  are  the  follow- 
ing: less  obstruction;  facility  and  saving  in  rail  transport; 
simpler  and  more  convenient  handling,  the  boiler  being 
abolished;  absolute  safety  and  therefore  complete  inde- 
pendence as  regards  official  inspection;  lessened  work  of 
maintenance;  no  disturbance  to  surface  on  starting. 

It  would  appear  that  these  light  rollers  comply  with 
the  new  ideas  regarding  mechanical  consolidation;  namely, 
that  the  binding  together  of  the  materials  must  be  sought 
in  bringing  about  their  juxtaposition  by  means  of  the  rolling 
action  and  not  by  weight  alone.  With  a  heavy  machine  a 
portion  of  the  work  expended  serves  no  better  purpose  than 
in  crushing  the  metalling,  more  especially  where  only  a  thin 
new  coating  is  spread. 

France.  C.  F.  J.  PELLE.  The  Salmson  and  Contant 
oil  driven  roller  was  first  tried  out  from  1903  to  1905.  It 
is  a  three- wheel  roller  weighing  from  17*/£  to  20  tons  and  is 
driven  by  an  oil  motor  of  25  to  30  horse-power.  Owing 
to  the  compactness  of  the  engine  the  makers  were  able  to 
bring  the  back  wheels  closer  together  so  that  the  front 
wheel  was  overlapped  by  each  back  wheel  about  12  inches  to 
14  inches.  The  results  obtained  with  this  roller  were  very 
satisfactory  so  far  as  the  facility  of  working  and  quality  of 
work  done  were  concerned.  The  only  fault  that  could  be 
found  with  it  was  that  the  motor  was  not  powerful  enough, 
especially  on  gradients  steeper  than  5  per  cent.  As  a  result 
of  some  trials  made  with  this  type  of  oil  engine  and  a  steam 


152  HIGHWAY   ENGINEERING 

roller  of  the  same  weight  on  recoating  work,  it  was  found 
that  a  saving  could  be  made  in  one  instance  in  favor  of  the 
oil  roller  of  about  23  per  cent,  and  in  other  instances  the 
cost  worked  out  about  the  same  for  the  two  rollers. 

The  Laffly  petrol  driven  roller  is  a  lighter  three  wheel 
roller  weighing  from  5^2  to  9  tons  and  is  driven  by  a  two 
cylinder  gas  engine,  which  develops  between  12  and  15 
horse-power.  The  back  wheels  overlap  the  front  wheels 
about  6  inches  on  either  side.  The  first  trials  with  this 
roller  were  made  in  1908  in  Paris,  where  its  work  was  com- 
pared with  the  work  done  by  a  3  ton  horse  roller.  The 
result  was  that  the  Laffly  roller  could  do  the  work  as  well 
and  in  a  much  quicker  time  at  a  saving  of  about  14  per 
cent.  In  figuring  the  cost  of  work  done  with  the  Laffly 
roller  overhead  charges  were  included.  Further  trials  with 
this  roller  were  made  in  repairing  isolated  patches  and  in 
constructing  roads  with  a  poor  subsoil  for  a  foundation. 
These  trials  showed  the  roller  to  be  particularly  efficient  for 
this  kind  of  work. 

Some  of  the  advantages  claimed  for  the  petrol  motor 
rollers  are  the  following: — 

1.  No  time  is  lost  in  waiting  to  get  up  steam  and  no 
cartage  is  required  in  supplying  the  roller  with  either  fuel 
or  water,  as  is  the  case  with  the  steam  roller. 

2.  The  rollers  are  less  noisy,  are  smokeless,  and  are 
capable  of  much  more  rapid  movement. 

3.  They  are  much  more  compact  and  hence  are  able 
to  work  to  better  advantage  on  roads  where  the  passage  of 
other  vehicles  is  of  importance. 

4.  The  lighter  rollers  from  6  to  8  tons  in  weight  can  be 
used  in  building  roads  on  a  bad  subsoil  where  the  use  of  a 
heavy  steam  roller  would  be  impossible. 


ROAD   MACHINERY  AND   TOOLS  153 

5.  They  are  particularly  useful  in  repairing  isolated 
patches  and  on  maintenance  work. 

France.  ALFRED  PONS.  Fault  has  been  found  with 
stone  crushers  on  account  of  the  tailings  that  get  in  with 
the  graded  sizes  of  the  stone.  The  writer  believes  that  the 
manufacturers  of  stone  crushers  should  give  their  attention 
to  the  projections  on  the  jaws  so  as  to  ensure  more  uniformity 
in  the  shape  and  size  of  the  product. 

The  removal  of  dust  is  generally  accomplished  by 
means  of  brooms.  Where  the  layer  of  dust  is  thick,  the 
hand  push  broom  is  used.  In  order  to  stiffen  a  brush  of 
this  kind  a  series  of  rods,  which  encircle  the  brush  and  which 
can  be  shifted  up  or  down,  are  employed.  The  squeegee 
and  scraper  with  iron  blades  can  be  used  only  for  removing 
the  top  layer  of  dust  of  a  certain  thickness  without  touching 
the  surface  of  the  road.  In  the  open  country  these  tools 
are  not  employed  for  cleaning  the  surface  and  the  writer 
believes  that  a  hand  drawn  rotary  sweeper  would  be  a  much 
better  device. 

For  several  years  past  sweeping  and  watering  have  been 
combined  in  one  machine.  As  soon  as  the  dust  has  been 
picked  up  by  the  revolving  brush  it  is  moistened  by  a  fine 
water  spray  which  prevents  its  being  scattered  broadcast. 
In  Germany  and  in  Belgium  sweeping  machines  are  em- 
ployed which  deliver  all  of  the  sweepings  carried  into  a  chest 
by  means  of  an  elevator.  Some  have  not  been  successful, 
although  the  principle  should  offer  some  advantages.  The 
sweeping  machines  best  adapted  for  thoroughly  cleaning 
smooth  paving  are  those  provided  with  a  roller  brush  of 
bamboo  or  fibre,  to  which  are  fitted  scrapers  with  rubber 
blades,  which  can  be  raised  or  lowered  by  means  of  a 
special  lever.  Both  simple  sweeping  machines  and  those 


154  HIGHWAY   ENGINEERING 

having  a  watering  attachment  have  been  fitted  with 
motor  power. 

Of  late  years  large  towns  have  tried  automobile  water 
carts  of  the  steam  or  petrol  driven  type.  The  capacity  of 
the  motor  water  carts  does  not  usually  exceed  790  gallons. 
The  spray  is  placed  near  the  front  of  the  carriage  so  that  the 
watering  is  always  under  the  eye  of  the  driver.  Another 
advantage  of  this  arrangement  is  that  as  the  machine  rides 
over  the  road  it  has  just  watered,  it  does  not  raise  any  dust. 

Scarifiers  have  been  economically  used  to  break  up  the 
old  surface  of  the  roads.  The  Bobe  scarifier  can  be  drawn 
either  by  road  roller  or  by  any  other  tractor  weighing  at 
least  10  tons.  The  apparatus  consists  of  a  solid  body  of 
channel  iron  carried  on  two  wheels  and  supporting  by  the 
axle  the  cast  iron  block  holding  the  three  steel  picks,  which 
are  placed  on  an  angle  and  which  can  be  regulated  so  as 
to  scarify  or  break  up  the  surface  to  any  desired  depth. 
As  the  machine  is  borne  only  on  two  wheels,  two  cast  iron 
discs  are  fastened  on  the  side  frames  and  act  as  counter- 
poises, thus  ensuring  equilibrium.  The  picks  are  brought 
in  contact  with  the  ground  automatically  and  are  similarly 
released.  From  trials  made  in  Paris  it  appears  that  the 
Bobe  machine  can  scarify  48  square  yards  of  any  solid 
porphyry  metalling  in  an  hour  at  a  cost  of  5.6  cents  per 
square  yard.  The  cost  is  much  less  with  sandstone  metal. 
In  some  instances  the  machine  was  able  to  break  up  210 
square  yards  an  hour  at  a  cost  of  only  2.05  cents  per  square 
yard.  The  Morrison  scarifier  is  manufactured  by  Messrs. 
Aveling  and  Porter.  Its  essential  parts  consist  of  a  wrought 
iron  frame  and  of  a  block  to  which  are  fitted  the  picks, 
which  by  means  of  a  lever  can  turn  round  a  horizontal  axis. 
The  block  can  be  raised  vertically  by  means  of  a  wheel 


ROAD   MACHINERY   AND   TOOLS  155 

and  thus  be  adjusted  to  any  desired  position.  This  machine 
can  be  worked  either  in  tow  of  the  roller  or  pushed  by  it. 

Various  machines  of  the  plough  type  are  in  use  for 
cleaning  the  shoulders  and  ditches.  Most  of  these  are 
drawn  by  animals.  The  blades  and  wheels  are  so  arranged 
that  the  ditches  can  be  readily  cleared  as  the  machine  is 
drawn  along  the  road. 

France.  CASIMIR  VERGER.  The  scarifiers  of  the  City 
of  Paris  belong  to  the  three  following  categories:— 

1.  Scarifiers  attached  direct  to  a  steam  roller,  such  as 
the  Morrison  type.     These  are  not  suitable  for  hard  road- 
ways.    The  scarifying  is  irregular  and  the  tractor  deterio- 
rates rapidly. 

2.  Towed  scarifiers,   such  as  the  Zettelmeyer  type. 
This  type  of  machine  performs  good  work  on  roadways  of 
medium  hardness  but  it  still  has  many  imperfections  as 
regards   hard   roads,   where   it   overturns   and  may  cause 
accidents  in  consequence  of  the  fracture  of  the  chain.     These 
machines  cannot  be  used  for  breaking  up  the  roads.     The 
long  chain  avoids,  however,  the  passage  of  the  roller  over 
the  surface  already  prepared. 

3.  Coupled  scarifiers,   such  as  the  Bobe  type,   have 
given  excellent  results.     The  safety  of  the  public  is  secured 
and  the  scarifying  is  regular.     They  break  up  the  road  to 
the  depth  of  1  foot  in  one  cut,  when  the  roadway  has  been 
well  watered.     The  distribution  of  shocks,  which  operate 
on  a  great  number  of  points,  diminishes  the  deterioration 
of  the  tractor.     After  three  years  of  extensive  work  with 
these  scarifiers  the  steam  rollers  do  not  show  any  trace  of 
damage.     The  steam  roller  travels  each  time  over  a  certain 
section  already  scarified,  but  this  inconvenience  is  not  of 
great  importance. 


156  HIGHWAY  ENGINEERING 

The  first  cost  of  scarifying  with  the  Bobe  and  Zettel- 
meyer  machine  is  the  same.  The  surfaces  treated  per  hour 
are  about  the  same  for  both  types  and  steam  rollers  of  14 
to  15  tons  weight  suffice  to  draw  each  of  them. 

At  Paris  the  preference  is  given  to  the  coupled  scarifiers, 
the  scarifiers  towed  with  a  chain  having  been  reserved  for 
metalling  of  a  moderate  hardness. 

Whatever  the  type  of  scarifier,  the  cost  per  square  yard 
of  mechanical  scarifying  (on  an  average  of  2.2  cents  to  2.8 
cents,  all  charges  included)  is  below  that  of  hand  picking 
(2.4  cents  to  6.5  cents).  In  a  day  of  eight  hours  1,800 
square  yards  can  be  scarified,  and  when  the  road  has  been 
moistened  several  days  in  advance  it  is  possible  to  attain 
as  high  as  2,900  square  yards  or  even  more. 

In  comparing  the  work  done  by  motor  driven  and  horse 
drawn  machines  for  cleaning  and  watering  the  writer  has 
reached  the  following  conclusions:— 

1.  The  average  amount  of  surface  swept  by  a  petrol 
motor  driven  machine  at  Paris  varies  from  14,352  to  17,940 
square  yards  (3  to  3.7  acres)  per  hour.     These  surfaces  are 
four  times  greater  than  those  covered  by  horse  drawn 
machines. 

2.  The  average  amount  of  surface  watered  with  steam 
or  petrol  driven  watering  carts  varies  from  21,528  to  34,086 
square  yards  (4.4  to  7  acres)  per  hour,  about  three  times 
greater  than  the  surface  watered  by  a   one  horse   drawn 
water-cart. 

3.  The  quality  of  the  work  done  is  equally  good  with 
either  motor  driven  or  horse  drawn  machines. 

4.  The  daily  expenses  per  acre  for  sweeping  or  watering 
by  motor  driven  machines,  although  below    those    corre- 
sponding for  horse  drawn  machines,  are  still  too  costly  on 


ROAD   MACHINERY   AND   TOOLS  157 

account  of  the  charges  for  sinking  fund  and  repairs.  It  is 
possible  to  reduce  these  charges  by  simplifying  the  mechan- 
ism, and  strengthening  the  working  parts. 

5.  The  motor  driven  water-cart,  made  exclusively  for 
watering,  has  a  very  limited  use  during  a  few  months  only. 
This  disadvantage  can  be  avoided  by  attaching  an  easily 
detachable  roller  brush.  The  weight  of  the  machine  is 
increased  by  this  addition  only  661  pounds,  which  is  of  no 
importance.  The  apparatus,  if  provided  with  a  removable 
tank,  may  be  transformed  into  a  lorry  for  transportation 
purposes. 

Great  Britain.  H.  T.  WAKELAM.  Petrol  motor  driven 
rollers  have  now  been  in  use  in  connection  with  road  work 
for  about  five  years.  The  back  roller  is  usually  3  feet  in 
diameter  and  4  feet  wide.  The  total  weight  of  the  smaller 
type  is  6^2  tons  empty  and  7J/4  tons  loaded.  Some  types, 
however,  weigh  12  tons.  The  consumption  of  petrol  varies 
from  about  l/3  of  a  gallon  an  hour  for  the  smaller  types  to 
l/€  gallons  an  hour  for  the  larger  sizes.  The  roller  is  usually 
speeded  to  1  and  3  miles  an  hour  when  the  engine  is  running 
normal.  It  is  possible  to  vary  the  engine  speed  above  or 
below  the  normal  by  a  hand  controller.  The  roller  is  driven 
by  chain.  The  wheels  are  generally  of  the  same  width  and 
run  tandem  fashion. 

The  working  charges  for  operating  a  5  ton  motor 
roller  are  at  the  rate  of  about  3.2  cents  an  hour  including 
wages,  petrol,  stores  and  repairs  which  amount  to  about 
24.4  cents  per  working  day.  This  size  of  roller  will  con- 
solidate about  3,000  square  yards  of  tarred  materials  on 
footpaths  in  a  working  day  of  eight  hours'  duration.  In 
rolling  tarred  macadam  on  carriageways  the  quantity  rolled 
is  reduced  owing  to  the  interference  of  other  traffic,  and  it 


158  HIGHWAY   ENGINEERING 

also  varies  with  the  rates  of  the  supply  and  quality  of  the 
materials  consolidated. 

Italy.  EMILIO  GOLA.  A  new  machine  to  which  the 
writer  would  like  to  call  attention  is  the  Guerrini  motor 
hopper  sweeper.  At  the  first  trials  made  in  January, 
1909,  at  Milan  and  Turin,  excellent  results  were  obtained. 
The  machine  lifted  off  the  road  all  sorts  of  material, 
whether  light  or  heavy,  and  deposited  them  directly  in 
the  hopper. 

The  machine  and  brush  are  driven  by  a  30  horse-power 
four  cylinder  motor  with  chain  drives.  Three  speeds  and 
a  reverse  are  provided.  A  special  device  ensures  a  constant 
relative  speed  of  the  brush.  The  brush  is  4.2  feet  in  diameter 
and  is  made  up  of  twenty  parts  arranged  lengthwise  of  the 
cylindrical  surface.  An  arrangement  is  provided  so  that 
when  brushes  get  worn  down  they  may  be  set  out  a  little 
in  their  bearings,  it  being  possible  to  continue  this  process 
until  practically  the  whole  length  of  fibre  in  the  brush  is 
worn  out.  The  cylinder  to  which  all  of  these  small  rotary 
brushes  are  attached  is  set  just  in  front  of  the  hind  wheels 
of  the  machine.  It  revolves  under  a  wrought  iron  cover 
open  at  the  bottom  and  provided  with  a  rectangular  opening 
at  the  top.  The  sweepings  are  picked  up  by  the  brushes 
and  thrown  by  centrifugal  force  through  the  opening  of 
the  wrought  iron  cover  into  a  chest  which  is  fixed  behind 
the  rear  wheels  and  which  holds  over  a  cubic  yard.  Doors 
are  provided  in  the  back  of  the  chest  so  that  the  sweepings 
can  readily  be  removed.  The  width  covered  by  the  sweeper 
is  5  feet.  At  a  speed  of  7.5  miles,  about  21,500  square  yards 
can  be  swept  in  an  hour. 

Russia.  CESLAV  WAICHT.  The  implements  used  in 
Russia  for  road  repairs  are  divisible  into  three  classes  accord- 


ROAD   MACHINERY   AND   TOOLS  159 

ing  to  the  work  they  perform;  namely,  rollers,  scarifiers, 
and  mud  and  dust  sweepers. 

At  the  present  time  horse  drawn  rollers  are  used  in 
resurfacing  75  per  cent  of  the  Empire's  roads.  The  first 
steam  rollers  for  road  repairing  in  the  Warsaw  district  were 
of  the  Aveling  and  Porter  type  and  were  imported  from 
England  in  1877.  Since  1890  several  works  have  been 
established  in  Russia  at  which  various  types  of  rollers  a're 
manufactured. 

Mechanical  scarifiers  have  not  been  much  used  as  yet 
in  Russia.  The  "Econome"  scarifier  designed  by  the  writer 
has  been  used  with  great  success  for  the  past  three  years, 
four  horses  furnishing  sufficient  power  for  its  successful 
operation.  With  this  machine  a  single  central  blade  is 
first1  set  to  work  and  with  it  parallel  furrows  are  made  in  the 
old  surface  12  inches  to  16  inches  apart,  after  which  the 
two  other  blades  are  brought  into  use  and  with  the  three 
blades  the  whole  surface  to  be  recoated  is  easily  scarified. 

Road  sweeping  has  been  done  by  manual  labor  in 
Russia  up  to  the  present  time,  but  machines  have  been 
tried  out  to  a  limited  extent  with  very  favorable  results. 

United  States.  ARTHUR  H.  BLANCHARD.  The  tar 
coating  machine  manufactured  by  the  American  Tar 
Company  has  been  used  in  Rhode  Island  to  mix  refined 
tar  with  cold  broken  stone  and  has  accomplished  excellent 
results  on  work  under  the  direction  of  the  writer.  This 
machine  consists  essentially  of  a  long  trough,  with  an  incline 
at  each  end,  equipped  with  a  fire  box  and  mounted  on  wheels. 
Under  the  middle  portion  of  the  trough  three  hot  air  pipes 
pass  through  a  bath  of  bituminous  material.  The  cold 
material  is  introduced  in  either  of  the  jackets  on  the  sides 
of  the  trough,  which  jackets  form  a  continuation  of  the 


160  HIGHWAY   ENGINEERING 

compartment  beneath  the  trough.  The  cold  material 
naturally  goes  to  the  bottom  of  the  bath  while  the  hot 
bituminous  material  rises  in  the  jackets  and  flows  into  the 
trough  through  holes  in  the  inside  walls  of  the  jackets. 
Cold  stone  is  placed  on  the  incline  furthest  from  the  work 
and  raked  from  there  into  the  hot  bituminous  material  and 
then  onto  the  other  incline  under  which  there  is  a  hot  air 
bath,  by  aid  of  which  superfluous  bituminous  material  is 
drained  from  the  coated  metal.  It  would  be  advantageous 
if  the  incline  on  which  the  cold  stone  is  first  placed  had  a 
hot  air  jacket  beneath  it,  in  order  that  the  stone  could  be 
slightly  heated  before  being  raked  into  the  bituminous 
material.  This  is  especially  pertinent  if  work  is  to  be  done 
after  the  first  of  October  and  if  compounds  containing  an 
asphalt,  solid  at  ordinary  temperatures,  are  used  as  binders. 
With  refined  coal  tars  the  machine  worked  very  satisfac- 
torily and  proved  very  economical  in  manipulation  during 
the  usual  working  season. 


> 

CHAPTER  XVI 

GARBAGE   REMOVAL,   CLEANING  AND  WATERING 

BALLO,  ALFRED,  Commissioner  of  Street  Cleaning, 
Budapest,  Hungary. 

BERTHET,  E.,  Councilor  of  State,  Monaco. 

BRET,  E.,  Chief  Engineer  of  Bridges  and  Roads,  Paris, 
France. 

HOPFNER,  PAUL,  Imperial  and  Municipal  Commissioner 
of  Public  Works,  Cassel,  Germany. 

KELLNER,  DR.  HANS,  Director  of  Public  Works,  Briinn, 
Austria. 

ROSHAUW,  J.  C.,  Director  of  Highways,  Christiania, 
Norway. 

SPTTERI,  JOSE  RODRIGUEZ,  Chief  Engineer  of  Highways, 
Canals  and  Harbors,  Malaga,  Spain. 

YABBICOM,  THOMAS  H.,  M.  Inst.  C.  E.,  City  Engineer, 
Bristol,  England,  Great  Britain. 

Austria.  DR.  HANS  KELLNER.  The  frequent  watering 
of  wood  pavements  is  considered  detrimental  because  the 
constant  change  from  a  wet  to  a  dry  condition  causes  the 
wood  to  deteriorate.  Watering  is  considered  very  necessary 
for  a  macadam  road  because  of  its  tendency  to  preserve  the 
road  in  dry  weather. 

In  cleaning  the  jointless  surface  streets  and  the  ordinary 
pavements,  the  primitive  method  of  sweeping  with  hand 

161 


162  HIGHWAY   ENGINEERING 

brooms,  the  collection  of  the  sweepings  by  means  of  shovels 
and  wheelbarrows  into  heaps  that  are  later  loaded  into 
collecting  carts  is  employed.  Specially  designed  sweeping 
plants  may  often  be  used  with  great  advantage.  These 
consist:  (a)  of  light  frames  bearing  portable  cans,  gener- 
ally made  of  iron,  with  facilities  for  the  carriage  of 
everything  that  the  workman  requires  (broom,  shovel, 
scraping  tools,  etc.) ;  (b)  of  a  platform  wagon  upon  which 
the  cans  taken  from  the  frames  can  be  easily  and  safely 
placed.  Each  plant  should  be  provided  with  a  sufficient 
number  of  cans  so  that  the  men  sweeping  will  not  be  de- 
layed for  the  lack  of  empty  cans.  The  filled  cans  are  re- 
moved on  the  platform  wagons  and  empty  cans  are  left. 
As  soon  as  the  wagon  is  fully  loaded  it  is  brought  to  the 
sweepings  depot  to  discharge  its  load  and  then  proceeds 
again  on  its  rounds  with  the  emptied  vessels.  This  kind 
of  cleaning,  of  course,  requires  a  careful  study  of  the  local 
conditions  and  a  correct  distribution  of  the  workmen,  so 
that  neither  the  sweeper  nor  the  collecting  wagon  is  idle. 

Sweeping  machines  are  being  introduced  more  and 
more.  Sweeping,  however,  is  considered  insufficient  to 
remove  all  dust  or  mud,  and  hence  it  is  necessary  to  resort  to 
washing. 

Water-carts  drawn  by  horse  or  propelled  by  steam  or 
gasoline  are  now  in  use,  the  methods  of  distribution  of  water 
being  by  means  of  turbine  wheels,  rose  pipes,  swinging  hose 
pipes,  etc. 

France.  E.  BRET.  The  removal  of  house  refuse  is 
accomplished  by  placing  garbage  cans  on  the  highway  one 
hour  before  the  time  of  collection  and  removing  them 
immediately  at  the  appointed  time.  A  practice  which 
should  be  stopped,  because  of  the  scattering  about  of  the 


GARBAGE   REMOVAL,    CLEANING   AND   WATERING        163 

refuse  to  some  extent,  is  the  sorting  over  by  the  poor  of  the 
garbage  in  the  cans  after  they  have  been  placed  on  the  high- 
way. Sweeping  should  be  done,  as  is  not  always  the  case, 
after  the  collection  of  the  garbage. 

In  the  majority  of  towns  the  sweeping  of  foot  pavements 
is  left  to  the  householder.  As  these  latter  are  particularly 
interested  in  the  cleanliness  of  the  foot  pavement,  this 
method  of  procedure  has  usually  no  disadvantages,  except 
that  in  wet  weather  if  the  pavements  are  not  swept  they 
become  muddy.  In  Paris  the  sweeping  of  the  footways  is 
done  by  the  nmnicipal  workmen  and  workwomen  commen- 
cing at  4: 00  A.  M.,  so  as  not  to  disturb  the  foot  traffic  and  to 
reduce  the  dust  nuisance.  When  necessary,  the  mud 
scraping  of  the  footways  is  carried  out  in  the  day  time. 
In  certain  towns,  for  instance  Orleans,  the  house  proprietors 
have  the  choice  between  carrying  out  the  work  themselves 
and  paying  a  tax. 

Sweeping  is  considered  insufficient  to  entirely  remedy 
the  evils  of  dust  and  mud,  and  hence  the  washing  of  pave- 
ments and  mud  scraping  are  common  in  connection  with 
sweeping.  Some  of  the  wood  pavements  of  Paris  are 
washed  daily.  Usually  the  washing  consists  of  an  ample 
watering  at  two  separate  intervals,  allowing  the  water  time 
to  act,  followed  by  a  sweeping  if  the  pavement  is  stone 
block,  or  by  squeegeeing  with  a  rubber  squeegee,  if  the 
pavement  is  asphalt  or  wood.  The  quantity  of  water  re- 
quired varies  from  0.11  of  a  gallon  to  0.22  of  a  gallon  per 
square  yard  for  asphalt,  0.22  to  0.44  of  a  gallon  for  wood, 
and  increasing  to  0.44  to  0.66  of  a  gallon  for  stone 
pavement.  Hose  washing  gives  the  best  results,  but  can 
be  used  only  in  towns  with  an  abundant  water  supply. 
Rain  is  usually  depended  upon  to  wash  sidewalks,  but 


164  HIGHWAY   ENGINEERING 

in  dry  weather  resort  is  made  to  washing  them  by  arti- 
ficial means. 

In  many  places  the  piles  of  sweepings  are  made  at  the 
side  of  the  street  or  in  the  gutters  and  are  either  removed 
in  dust  wagons  or  flushed  into  the  sewers.  The  gutters 
in  some  cities  are  flushed  twice  a  day  to  remove  products 
of  road  sweeping  or  dirty  water  from  the  houses.  The 
flushing  of  gutters  is  often  left  to  the  proprietors  who  do  it 
by  opening  hydrants,  but  this  method  lacks  concerted 
action. 

Watering  is  done  to  prevent  dust  rising,  but  care  should 
be  taken  that  this  is  not  done  to  excess. 

At  Paris,  the  number  of  daily  waterings  are  usually  dis- 
tributed thus: 

j  2  waterings  on  the  main  thoroughfares. 

April,  May,  Sept.,  Oct 1  . 

(  1  watering  on  the  secondary  streets. 

f  Pavements  3  waterings  on  the  main  thoroughfares. 

June,  July      j  "  2  waterings  on  the  secondary  streets. 

and  Aug.        ]  Macadam  3  to  4  waterings  on  the  main  thoroughfares. 

"  2  to  3  waterings  on  the  secondary  streets. 

It  is  occasionally  necessary  to  apply  water  in  March 
and  November. 

The  minimum  amount  of  water  to  be  daily  used  per 
square  yard  can  be  estimated  as  follows: 

Spring  and  Autumn  Summer 

Macadamized  roads. . .  0.20  of  a  gallon ....  0.40  of  a  gallon  per  square  yard. 

Wood  block  pavements  0.02      "       "     ....  0.22 

Stone  block  pavements  0.09      "      "     0.18 

Asphalt  pavements 0.07      "      "     0.13 

Germany.  PAUL  HOPFNER.  Sewers  are  seldom  made 
use  of  for  carrying  away  the  sweepings  because  of  the  large 
quantities  of  water  required  and  the  unquestionable  fact 


GARBAGE    REMOVAL,    CLEANING   AND   WATERING       165 

that  it  is  cheaper  to  cart  sweepings  away  rather  than  lead 
them  to  drains  and  later  before  they  reach  the  natural 
stream  to  have  to  remove  them. 

Where  the  main  part  of  the  work  is  done  by  night, 
sweepings  necessarily  taken  up  during  the  day  are  placed  in 
bins  on  footways  and  carted  off  at  night  in  connection  with 
the  regular  work.  The  wagons  used  are  not  covered  because 
the  materials  are  dampened  and  therefore  are  not  dusty. 

Machines  which  dampen,  sweep,  and  take  up  material 
have  been  used  but  have  not  proved  satisfactory.  It  is 
considered  better  as  far  as  the  results  secured  are  concerned 
to  use  water-carts  followed  later  by  horse  drawn  or  hand 
sweepers.  The  period  lapsing  between  the  watering  and 
the  sweeping  should  be  governed  by  the  condition  of  the 
weather.  Washing  machines  consisting  of  a  watering  tank 
equipped  with  rubber  rollers  to  drive  the  wet  mud  into  the 
gutters  are  used.  Footways  are  first  wet  by  hand  carts  or 
cans  and  then  cleared  by  hand  with  piassava  or  rubber 
brooms.  Automobile  water-carts  are  rare  as  are  also  tram- 
way watering  tanks.  The  water-cart  is  usually  horse 
drawn  or  more  rarely  hand  drawn. 

The  sweepings  are  used  quite  extensively  by  farmers 
for  fertilizer  and  hence  it  is  desirable  to  have  the  house  re- 
fuse and  street  sweepings  carried  off  separately.  Where 
the  demand  for  sweepings  for  fertilizing  purposes  is  not  so 
great,  use  is  made  of  them  for  grading  purposes  about  the 
city. 

Great  Britain.  THOMAS  H.  YABBICOM.  In  sixteen 
large  towns  making  reports  it  was  found  that  60  per  cent 
of  the  roads  are  macadam,  32  per  cent  stone  block  pave- 
ment, 3  per  cent  wood  block  pavement,  and  5  per  cent 
constructed  of  various  materials  including  asphalt.  From 


166  HIGHWAY   ENGINEERING 

the  above  percentages  it  is  evident  that  the  cleaning  of 
macadam  roads  is  of  the  greatest  importance  in  England. 

Reports  from  twenty  towns  showed  that  horse  drawn 
sweepers  are  used  in  fourteen,  while  in  the  remaining  six 
the  engineers  consider  that  they  damage  the  road  surface. 
Machines  to  sweep  and  load  in  one  operation  have  been 
used,  but  they  are  not  considered  practicable.  Attempts 
to  combine  watering  and  sweeping  in  one  machine  have  not 
proved  satisfactory,  the  general  practice  being  for  the 
water-cart  to  precede  the  sweepers.  Main  streets  are 
swept  daily  and  secondary  streets  are  swept  three  times  a 
week.  In  most  cases  sweepers  are  kept  constantly  at 
work,  the  sweepings  being  placed  in  bins  which  are  either 
above  or  below  the  surface  of  the  pavement.  Later  these 
bins  are  emptied  into  wagons,  the  material  being  carted 
away  and  either  dumped  into  the  rivers  or  sold  or  given  to 
farmers  for  fertilizers. 

The  water  used  for  watering  streets  is  paid  for  by 
volume,  by  lump  sum  per  year,  or  it  is  obtained  free.  In 
all  but  two  towns  the  water-carts  are  horse  drawn.  At 
present  there  is  a  tendency  to  replace  the  water  barrels  on 
the  carts  by  rectangular  tanks.  The  general  practice  now 
is  to  use  tanks  giving  a  small  flow  or  spray.  It  is  believed 
that  continuous  watering  decomposes  macadam. 

Hungary.  ALFRED  BALLO.  In  Budapest  the  city 
cleans  the  roads,  and  the  property  owners  the  sidewalks. 
The  cleaning  is  done  almost  entirely  by  hand,  each 
sweeper  having  to  take  care  of  an  area  of  about  6,207  square 
yards  on  an  average.  The  sweepings  are  collected  in  cars 
and  taken  to  stations  where  carts  are  in  readiness  to  take  the 
material  away.  The  transfer  to  the  carts  has  of  late  been 
done  in  a  closed  room  to  prevent  the  spreading  of  the  dust. 


GARBAGE    REMOVAL,    CLEANING   AND   WATERING         167 

There  is  in  this  room  also  a  reinforced  concrete  tank,  capable 
of  being  hermetically  closed,  into  which  any  surplus  sweep- 
ings are  placed. 

The  dust  carts  are  built  of  iron,  each  with  a  bin  holding 
6J/£  cubic  yards.  They  carry  the  sweepings  to  a  railway 
station  situated  outside  the  inhabited  part  of  the  town  and 
built  expressly  for  this  purpose.  Here  a  large  electric 
traveling  crane  lifts  the  full  dust  cart  bins  from  the  trucks 
without  touching  their  contents,  and  exchanges  them  for 
empty  ones.  The  full  bins  are  then  placed  by  this  crane 
onto  the  railway  cars,  on  which  they  are  brought  to  the 
refuse  factory  to  be  emptied.  Here  the  sweepings  from  the 
streets  are  combined  with  fecal  substances  and  sold  as 
manure  for  agricultural  purposes. 

Asphalt  streets  are  washed  in  summer  to  some  extent  by 
hand  or  machine.  The  machines  used  are  water-carts  equipped 
with  rollers  or  some  other  device  to  displace  the  mud. 

Although  owners  are  supposed  to  keep  sidewalks  clean, 
boys  from  twelve  to  sixteen  years  of  age  are  employed  to 
collect  large  articles  of  waste  from  the  sidewalks. 

About  one-fourth  of  the  street  area  is  watered  from 
hydrants  and  the  remainder  by  water-carts.  The  water-carts 
are  mostly  of  the  old  perforated  tube  type,  but  are  being 
replaced  more  and  more  by  those  of  the  valve  cylinder  type. 

Monaco.  E.  BERTHET.  In  Monaco  the  street  clean- 
ing is  done  entirely  by  hand  and  with  great  thoroughness. 
Household  refuse  is  carried  away  in  carts  between  six  and 
eight  o'clock  in  the  morning  and  the  material  is  burned  in 
a  destructor  of  the  Horsfall  type.  These  carts  are  washed 
and  disinfected  daily.  Dust  and  horse  dung  is  removed  by 
portable  scoop  shovels  and  carried  to  bins  which  are  built 
on  the  sidewalk  and  covered  with  foliage  or  beneath  the 


168  HIGHWAY   ENGINEERING 

surface  of  the  pavement,  or  it  is  placed  in  portable  cans. 
The  wagons  collect  the  sweepings  from  the  various  recep- 
tacles when  they  pass.  The  bins  and  cans  are  regularly 
disinfected.  Chloride  of  lime  is  spread  over  the  bins  during 
the  heat  of  the  day  in  summer. 

The  mud  is  collected  by  a  scraper  and  the  liquid  mud 
is  collected  by  means  of  a  scoop,  an  operation  which  rarely 
has  to  be  performed  at  Monaco.  When  a  slight. rain  occurs, 
a  thorough  road  washing  generally  insures  a  sufficient 
cleansing.  All  road  sweepings  are  deposited  at  the  public 
depots  and  covered  up  with  rubbish,  thus  preventing  all 
emanations. 

Besides  the  corps  of  sweepers  who  are  engaged  in  fixed 
duties,  there  is  a  flying  column  controlled  by  an  overseer. 
The  functions  of  the  flying  column  are:  the  care  of  the 
torrent  beds,  ponds  and  lavatories;  the  removal  of  seaweed 
blown  on  the  shore;  the  cleaning  of  the  foreshore  and  beach; 
the  disinfection  of  certain  localities,  corners,  blind  alleys, 
etc.  One  man  is  specially  in  charge  of  the  cleaning  of 
lavatories  and  two  men  are  attached  to  the  French  Depart- 
ment of  Bridges  and  Roads  in  order  to  insure  the  cleanliness 
of  the  National  Highway,  Number  7,  on  the  immediate 
frontier  of  the  Principality. 

Watering  is  done  by  means  of  hose  pipe,  because  such 
apparatus  is  considered  less  cumbersome  than  a  water-cart. 

The  239,200  square  yards  of  surface  swept  and  cleaned 
costs  $2,702  per  annum,  not  including  the  cost  of  the  water. 

At  certain  places  the  night  dampness  renders  the  road 
slippery.  This  defect  is  remedied  in  winter  by  spreading 
clean,  fine  sea  sand  over  the  road  at  such  places  as  may 
require  it.  This  sand  is  stored  in  bins  under  the  foot  pave- 
ment or  concealed  in  some  other  way. 


GARBAGE   REMOVAL,    CLEANING   AND   WATERING        169 

Norway.  J.  C.  ROSHAUW.  In  Christiania  ordinary 
sweeping  is  accomplished  by  horse  sweepers  and  by  hand, 
although  the  former  method  has  proved  to  be  more  satis- 
factory. Combined  sweepers  and  sprinklers  are  not  practi- 
cable because  they  are  too  heavy  for  the  steep  grades  en- 
countered. Macadam  roads  are  scraped  in  wet  weather. 
Streets  are  watered  immediately  before  sweeping  by  means 
of  water-carts  with  turbine  or  tube  distributors.  The 
latter  type  is  preferred.  Ordinary  sweepings  are  usually 
taken  out  in  the  bays  and  dumped,  while  sweepings  from 
paved  streets  are  employed  for  fertilizer. 

Besides  the  ordinary  sweeping  of  roads,  which  is  carried 
out  under  normal  conditions,  in  accordance  with  the  traffic 
of  the  streets,  from  one  to  six  times  a  week,  workmen  are 
continually  employed  in  the  main  streets  to  collect  the  horse 
droppings,  in  order  that  the  streets  may  always  present  a 
clean  appearance.  These  workmen  are  supplied  with  a 
light  wheelbarrow,  the  contents  of  which  they  empty  into 
small  galvanized  iron  bins,  provided  with  covers,  and  placed 
at  convenient  distances  along  the  street.  These  bins  are 
emptied  into  the  receiving  carts.  The  contents  thus 
collected  are  transported  elsewhere,  and  finally  are  sold  to 
the  gardeners  and  peasants  at  a  profit. 

Spain.  JOSE  RODRIGUEZ  SPITERI.  The  soil  absorbs 
the  germs  of  all  infectious  diseases  of  both  human  beings  and 
animals  and  in  the  densely  populated  cities  it  contains  a 
greater  number  of  them  than  in  the  country  districts. 
Fraenkel  has  found  that  the  soil  of  Berlin  contains  450,000 
germs  per  cubic  centimeter;  according  to  Miquel  the  mud 
of  Paris  streets  contains  1,000  millions  of  them  and  that  of 
Montsouris  Park  only  10  millions;  while  Maggiora  has 
found  32  millions  in  the  soil  of  Turin. 


170  HIGHWAY   ENGINEERING 

Cleansing  and  watering  are  both  largely  done  by  hand, 
this  method  being  the  only  one  applicable  to  narrow,  tortuous 
streets.  The  work  should  be  done  after  midnight  so  that 
traffic  will  be  interfered  with  as  little  as  possible.  The 
horse  droppings  and  litter  of  various  sorts  must,  however, 
be  removed  during  the  day. 

In  hot  countries  a  pressure  tank  which  sends  forth  a 
fine  spray  is  very  desirable  because  of  the  great  saving  in 
the  amount  of  water  used.  Where  such  installations  do 
not  exist,  one  has  to  be  content  with  ordinary  hydrants  and 
with  public  fountains  which  have  to  be  fitted  with  some 
special  arrangement  for  filling  the  water-carts.  In  harbors 
and  seaside  towns  sea- water  is  used.  It  is  drawn  up  by 
portable  pumps  and  sometimes  even  by  hand  with  buckets. 
It  is  needless  to  remark  that  where  such  conditions  prevail, 
and  unfortunately  such  instances  are  still  very  numerous, 
the  work  of  street  watering  is  done  slowly  and  inefficiently. 
This  is  to  be  regretted  both  from  a  sanitary  point  of  view 
and  from  the  interest  of  the  public  comfort,  both  of  which 
demand  thorough  work.  The  cost,  under  these  conditions, 
is  excessive. 

The  writer  has  designed  a  horse  drawn  cylindrical  tank 
of  about  211  gallons  capacity  on  wheels,  which  is  fitted  with 
a  very  simple  device  by  means  of  which  the  tank,  when 
empty,  can  be  filled  in  five  minutes.  By  means  of  a  pump, 
worked  by  the  cart  wheels,  either  a  vacuum  or  a  compression 
can  be  obtained,  the  former  to  be  used  in  filling  the  tank  and 
the  latter  to  force  the  water  out  of  the  tank  onto  the  road  in 
a  very  fine  spray.  The  writer  expects  that  very  good  re- 
sults will  be  obtained  with  this  water-cart  although  he 
has  not  yet  been  able  to  try  it  out  in  actual  practice. 


CHAPTER  XVII 

REMOVAL  OF  SNOW  AND  ICE 

BRET,  E.,  Chief  Engineer  of  Bridges  and  Roads,  Paris, 
France. 

CINQUE,  VICTOR,  Chief  Engineer,  Province  of  Brescia, 
Italy. 

COURTOIS,  AUGUSTE,  Principal  Inspector  of  Bridges  and 
Roads,  Bastogne,  Belgium. 

HOPFNER,  PAUL,  Imperial  and  Municipal  Commissioner 
of  Public  Works,  Cassel,  Germany. 

MAZEROLLE,  L.,  Engineer  of  Bridges  and  Roads,  Paris, 
France. 

MIKHAILOFF,  PAUL,  Engineer  of  Highways,  St.  Peters- 
burg, Russia. 

ROSHAUW,  J.  C.,  Director  of  Highways,  Christiania, 
Norway. 

SPANGLER,  LUDWIG,  Municipal  Director  of  Streets, 
Vienna,  Austria. 

WILHELM,  IVAN,  Chief  Engineer  of  Bridges  and  Roads, 
Gap,  France. 

YABBICOM,  THOMAS  H.,  City  Engineer,  Bristol,  England, 
Great  Britain. 

Austria.  LUDWIG  SPANGLER.  In  the  city  of  Vienna 
the  snow  is  cleared  by  the  tramway  companies  which  are 
at  the  present  time  all  owned  by  the  municipality.  When 
the  cars  were  drawn  by  horses  it  was  a  very  easy  matter  to 

171 


172  HIGHWAY   ENGINEERING 

clear  the  snow  by  means  of  horse  drawn  plows.  With  the 
advent  of  electric  traction,  the  procuring  of  sufficient  horses 
to  draw  the  plows  was  attended  with  so  much  delay  that  the 
city  authorities  turned  their  attention  to  the  use  of  snow- 
plows  driven  by  the  cars. 

In  general  the  method  employed  in  the  removal  of  the 
snow  from  the  streets  in  Vienna  is  as  follows: 

1.  The  removal  of  the  snow  from  the  track  by  means 
of  snow-plows  driven  by  horses  or  by  tramcars. 

2.  The  shovelling  of  the  snow  into  heaps  along  the  edges 
of  the  footways  by  hand. 

3.  The  removal  of  the  snow,  thus  collected,  by  carts. 
Wherever  the  car  tracks  lie  in  the  middle  of  the  road  the 

whole  roadway  is  cleared  of  snow  in  the  following  manner. 
Two  snow-plows  are  coupled  to  the  car  and  are  drawn  along 
the  roadway  to  one  side  of  the  track.  The  plows  are  plat- 
forms mounted  on  four  wheels  and  underneath  the  plat- 
forms are  a  series  of  horizontal  rods  to  which  are  attached 
vertical  blades  or  shovels,  capable  of  being  raised  or  lowered. 
When  the  plows  are  used  in  pairs  one  is  drawn  along  to  one 
side  and  just  behind  the  other  in  such  a  way  as  to  clear 
two  widths  at  one  passage.  These  plows  can  be  run  at  a 
speed  of  about  7  miles  per  hour.  The  car  itself  is  fitted  with 
a  series  of  blades  which  clears  the  snow  from  the  track  at 
the  same  time  the  roadway  is  being  cleared  by  the  two 
auxiliary  plows.  The  snow  is  removed  in  this  manner  from 
half  of  the  road  by  one  passage  of  the  car  and  plows,  after 
which  it  is  removed  from  the  roadside  by  wagons.  The 
other  half  of  the  road  is  cleared  in  a  similar  manner. 

The  method  just  described  is  suitable,  however,  only 
for  a  comparatively  small  depth  of  snow.  With  greater 
depths  not  only  would  the  work  be  increased  to  such  an 


EEMOVAL    OF   SNOW   AND   ICE  173 

extent  that  the  ordinary  tramcar  would  not  be  sufficiently 
powerful  to  pull  the  snow-plows  through  the  snow,  but  the 
snow  would  accumulate  underneath  the  car  and  runners  as 
well  as  under  the  auxiliary  plows,  making  effective  working 
of  the  plows  impossible.  If  the  fall  of  snow  occurs  suddenly 
there  is  a  danger  that  it  will  become  impossible  to  pull  a 
snow-plow  through.  In  such  a  case  the  blades  must  first 
be  raised  a  few  inches  above  the  ground  so  that  only  the 
upper  layer  of  snow  is  at  first  removed,  the  rest  being  dealt 
with  on  a  second  journey.  The  most  important  point, 
however,  is  always  to  get  the  snow-plows  to  work  as  quickly 
as  possible. 

For  districts  in  which  the  snow  falls  rapidly  in  enormous 
quantities,  the  snow-plows  described  are  not  sufficient  and 
resort  has  to  be  made  to  apparatus  of  the  kind  used  on  the 
railways  consisting  of  high  plow  shaped  inclined  planes  which 
are  generally  fitted  to  special  cars  that  bore  their  way  into 
the  snow  throwing  it  off  the  track  to  one  or  both  sides. 
In  this  case  the  snow  must  be  removed  from  the  roadway 
by  other  means. 

For  clearing  the  track  of  snow  alone,  especially  in  out- 
lying districts,  rotary  brushes  are  attached  in  front  and  at 
the  rear  of  a  specially  designed  car.  The  result  obtained 
is  very  good,  the  snow  being  cut  away  and  thrown  to  the 
side  of  the  road,  but  for  a  very  deep  snow  this  machine 
cannot  be  used. 

Simultaneously  with  the  clearing  of  the  track  and  the 
roadway  the  rail  grooves  must  be  cleared.  For  this  purpose 
a  specially  designed  machine  called  a  rail  scratcher  is  used 
in  Vienna.  It  is  an  iron  frame  bearing  two  suitably  designed 
castings  which  fit  into  the  rail  grooves  and  cleans  them  as 
it  is  pushed  along  in  front  of  the  car. 


174  HIGHWAY   ENGINEERING 

For  the  roads  that  are  not  traversed  by  tram  lines,  the 
snow  removal  operations  are  not  managed  from  a  central 
point,  but  are  divided  into  districts.  Apart  from  the  fact 
that  the  operations  of  snow  removal  do  not  have  to  be 
started  as  early  in  the  day,  the  methods  employed  are 
similar  to  those  used  by  the  tramway  companies,  the  same 
style  of  plow  is  used  and  is  generally  followed  by  a  rotary 
sweeper. 

Due  to  the  fact  that  the  banks  of  snow  thrown  up  by 
the  snow-plows  must  be  shovelled  into  heaps  and  removed 
as  soon  as  possible,  it  is  very  important  that  the  necessary 
supply  of  workmen  be  available  soon  after  the  snow  begins 
to  fall.  For  this  reason  it  is  necessary  to  carefully  plan  out 
the  organization  early  in  the  season  so  that  the  work  may 
be  carried  on  without  any  unnecessary  delays. 

Belgium.  AUGUSTE  COURTOIS.  Although  the  use  of 
snow  fences  would  keep  the  snow  out  of  shallow  cuts,  such 
an  expediency  is  not  practical  in  road  work  through  popula- 
ted places,  due  not  only  to  the  objections  on  the  part  of  the 
roadside  inhabitants  but  also  to  the  great  cost  of  the  fences. 
It  is  seldom  that  the  snow  lies  in  a  layer  of  uniform  thickness, 
and  it  is  only  after  a  long  and  constant  fall  that  it  attains  a 
regular  thickness  of  10  inches.  Such  a  depth  of  snow  makes 
traffic  almost  impossible.  It  should  be  cleared  away  when 
it  reaches  a  thickness  of  4  inches  to  5  inches.  For  this 
purpose  a  snow-plow  is  brought  into  use  or  the  snow  is 
shovelled  off.  When  drawn  by  four  good  horses  snow-plows 
cannot  clear  away  continuous  layers  of  snow  over  10  inches 
to  12  inches  deep,  but  they  will  negotiate  banks  several  feet 
in  width  of  even  twice  that  depth.  When  the  layer  of  snow 
is  as  thick  as  or  thicker  than  2  feet  to  2^  feet  shovels  have  to 
be  used. 


REMOVAL   OF    SNOW   AND    ICE  175 

The  snow-plow  employed  in  the  Luxemburg  district 
consists  of  two  side  pieces  hinged  together  and  kept  apart 
at  variable  distances  by  removable  cross  pieces,  forming  a 
triangle.  The  plow  should  be  set  to  work  as  soon  as  the 
layer  of  snow  has  attained  a  depth  of  4  inches  and  the 
number  of  machines  used  should  be  such  that  none  of  them 
has  to  deal  with  more  than  about  6  miles. 

France.  E.  BRET.  On  account  of  the  heavy  expense 
which  the  removal  of  snow  demands,  it  is  left  on  the  roads 
in  many  towns  until  it  disappears  of  its  own  accord.  Such 
a  primitive  practice  is  irreconcilable  considering  the  re- 
quirements of  traffic. 

The  method  of  removing  snow  from  streets  is  generally 
to  clean  out  a  path  wide  enough  for  the  travel,  heaping  the 
snow  up  at  both  sides,  the  work  being  done  by  plows  or 
sweepers,  depending  upon  the  temperature  of  the  air  and 
the  amount  of  snowfall.  The  snow  is  then  carted  away  to 
the  rivers  or  sewers.  Snow-plows  of  the  common  triangular 
design,  of  the  simple  inclined  board  design,  and  of  the 
sectional  design  capable  of  following  irregular  surfaces  are 
in  common  use.  In  some  cities  the  snow  is  flushed  directly 
into  gutters  by  water  and  hence  to  the  sewers.  Salt  is  used 
to  melt  the  snow  quite  extensively  and  is  usually  considered 
practicable.  It  is  considered  the  best  practice  to  spread 
it  before  the  snow  is  trampled  down.  The  process  leaves 
only  mud,  which  may  readily  be  removed.  In  Lille  a 
mixture  of  one  part  salt  and  three  parts  sand  is  used  which 
prevents  slipperiness.  Some  municipalities  are  opposed 
to  the  use  of  salt,  on  account  of  the  icy  mud  formed,  and  the 
effects  on  shoe  leather  and  the  horses'  hoofs.  However, 
these  disadvantages  can  be  minimized  by  sweeping  the  streets 
as  soon  as  it  is  possible.  Salt  cannot  be  used,  however,  on 


176  HIGHWAY   ENGINEERING 

macadamized  roads  as  it  causes  disintegration.  The  same 
reservation  must  also  be  made  as  regards  foot  pavements 
with  trees,  on  account  of  its  harmful  action  on  the  roots. 
Steam  and  hot  water  have  been  employed  to  melt  snow,  but 
both  of  these  methods  are  considered  too  expensive. 

France.  L.  MAZEROLLE.  The  various  methods  of 
snow  removal  may  be  subdivided  into  two  particular  classes, 
removal  in  forms  of  heaps  or  banks  and  thawing  in  place. 
In  the  first  method  it  is  necessary  to  provide  for  the  removal 
of  the  heaps  which  have  been  formed  with  much  labor, 
whereas  in  the  second  the  water  rising  from  the  thawing  is 
naturally  directed  towards  the  sewers. 

At  present  in  the  City  of  Paris  the  work  of  snow  removal 
is  accomplished  as  follows:  As  soon  as  the  snowfall  occurs, 
workmen  of  the  administration  commence  at  once  to  salt 
the  roadways.  The  salt  begins  to  produce  a  thawing  action 
only  after  the  traffic  has  mixed  it  with  the  snow.  While 
waiting  for  this  effect  to  be  produced,  the  workmen  are 
employed  in  opening  up  footways  for  the  pedestrians  at 
the  road  crossings,  while  the  abutting  property  owners 
clear  the  foot  pavements  as  well  as  the  gutters.  The  sweep- 
ing machines  are  then,  brought  into  use  which  sweep  some 
of  the  liquidated  mixture  of  snow  and  salt  to  the  gutters. 
The  flushing  nozzles  are  then  used  and  the  heavy  accumu- 
lated snow  is  flushed  to  the  sewers,  for  which  purpose  the 
flushing  water  serves  as  the  vehicle.  When  the  thermom- 
eter remains  in  the  neighborhood  of  zero,  or  above,  the 
operation  thus  conducted  is  extremely  rapid,  but  if,  on  the 
contrary,  the  thermometer  remains  somewhat  below  zero, 
the  sweeping  of  the  snow  is  more  difficult  and  the  flushing 
to  the  sewers  is  prevented  for  fear  of  ice  forming.  Under 
the  latter  conditions  the  snow  is  removed  from  the  roadway 


REMOVAL   OF   SNOW  AND   ICE  177 

to  banks  at  the  side.  Afterwards  it  may  be  carried  away 
or  melted.  In  Paris  rock  salt  is  used,  selected  mainly  from 
the  standpoint  of  its  low  cost.  For  a  snowfall  of  about  1 
inch  about  0.18  of  a  pound  of  salt  is  used  per  square  yard. 
The  specification  for  the  salt  is  as  follows:  the  largest 
diameter  of  the  grains  of  salt  must  not  exceed  0.12  of  an 
inch;  the  proportion  of  fine  grains  passing  a  sieve  number 
25  shall  not  exceed  40  per  cent;  the  salt  shall  not  be  adul- 
terated. The  salt  is  usually  spread  by  throwing  from  a 
shovel.  Various  salting  machines,  consisting  of  a  hopper 
from  which  the  salt  escapes  and  falls  on  horizontal  revolving 
blades  which  throw  it  over  a  roadway  surface  of  a  width  of 
12  to  15  feet,  have  been  designed.  The  principal  objection 
to  these  machines  is  that  putting  the  machine  to  work  always 
requires  such  long  delays  that  it  is  by  no  means  certain  that 
the  loss  of  time  will  be  regained  later. 

The  use  of  machine  sweepers  gives  fair  results  in  the 
case  of  snowfalls  from  J/2  an  inch  to  1  inch  in  thickness.  A 
great  deal  of  trouble  has  been  experienced  in  using  rotary 
sweepers  in  having  the  bristles  get  choked  up  with  the 
snow  so  that  no  sweeping  action  is  performed.  Powerful 
machine  sweepers  running  on  the  rails  of  the  tramway  com- 
panies, the  brushes  of  which  are  operated  by  motor  power, 
have  given  very  good  results.  Whatever  machines  may  be 
employed,  their  action  is  the  most  efficacious  when  the  snow 
has  not  been  touched  by  the  traffic.  It  would  seem  that  the 
ideal  plant  for  the  removal  of  snow  would  consist  of  motor 
vehicles  fitted  in  front  either  with  scrapers  or  roller  brushes 
rotating  at  high  speed.  The  removal  of  the  snow  which 
has  been  swept  into  heaps  or  banks  at  the  sides  of  the  streets 
requires  a  large  amount  of  work.  Although  it  is  possible 
to  use  carts,  trains  of  small  cars  running  on  rails  of  tram- 


178  HIGHWAY   ENGINEERING 

ways  or  by  means  of  Decauville  tracks,  or  motor  lorries  to 
carry  the  snow  to  certain  discharge  depots,  it  is  clear  that 
the  cost  is  considerable.  Where  the  sewers  are  of  suffi- 
cient cross-section,  the  snow  may  be  discharged  directly  into 
them,  but  precautions  should  be  taken  against  blocking  the 
sewers. 

It  has  been  proposed  to  melt  the  heaps  by  steam  jets, 
electric  heaters  or  boilers,  but  as  yet  no  practical  apparatus 
has  been  designed  for  this  purpose. 

The  organization  of  the  service  for  the  removal  of  the 
snow  should  be  prepared  in  advance,  and  all  the  measures 
to  be  taken  should  be  provided  for  in  the  plan  of  mobiliza- 
tion, taking  into  consideration  the  various  local  circum- 
stances. 

France.  IVAN  WILHELM.  In  some  parts  of  France, 
more  especially  in  the  mountainous  regions,  frequent  heavy 
falls  of  snow  occur  which  necessitate  more  or  less  work 
in  the  way  of  removal  to  make  the  roads  passable  for  traffic. 
The  means  employed  vary  according  to  the  climate  and  the 
altitude.  In  regions  where  the  climate  is  not  very  severe, 
traffic  is  maintained  in  the  winter  time  by  passing  a  V-shaped 
snow-plow  over  the  road  occasionally.  The  plows  are 
started  whenever  the  snow  reaches  a  thickness  of  from  6 
inches  to  10  inches.  In  high  altitudes,  if  the  layer  of  snow 
is  thick,  other  measures  have  to  be  taken.  The  passage 
of  vehicles  must  first  be  provided  for  by  clearing  passing 
places  with  shovels. 

The  employment  of  snow-plows  is  only  possible  up  to 
a  certain  height,  this  altitude  in  the  Alps  varies  from  3,600 
feet  to  4,800  feet.  To  keep  the  road  open  for  traffic  in  these 
places  a  track  is  made  by  tramping  down  the  snow  with 
four  to  six  horses  travelling  abreast  after  which  the  track 


-  REMOVAL   OF    SNOW   AND    ICE  179 

is  widened  with  shovels.  The  methods  described  above 
are  carried  out  by  gangs  of  workmen  who  are  recruited  in  the 
neighboring  villages  and  are  under  the  direction  of  a  road 
foreman. 

Germany.  PAUL  HOPFNER.  Snow  is  removed  by 
collecting  it  into  piles  by  the  use  of  snow-plows  and  later 
carting  it  off  to  some  suitable  place  to  melt  or  to  dump  it 
into  the  rivers  or  sewers.  No  detrimental  results  ensue 
from  dumping  snow  into  the  sewers,  provided  there  is  a 
large  flow  of  water  and  if  care  is  taken  not  to  throw  in  too 
large  lumps. 

Great  Britain.  THOMAS  H.  YABBICOM.  Snow  is 
dumped  into  rivers  or  run  through  the  sewers.  Salt'  is 
used  to  some  extent,  but  the  practice  is  considered  injurious 
to  both  man  and  beast,  because  of  the  intense  cold  produced. 

Some  towns  have  local  Acts  of  Parliament  which  require 
the  householders  to  clear  the  snow  from  off  the  footways 
in  front  of  their  premises.  But  even  in  these  towns  there 
are  many  miles  of  footways  in  front  of  unoccupied  premises, 
public  buildings,  places  of  worship,  bank  walls,  on  bridges 
and  viaducts  where  the  paths  would  never  be  cleared  at 
all  unless  it  was  done  by  the  municipality.  In  some  towns 
the  authorities  undertake  the  whole  duty.  The  snow,  when 
cleared  from  the  path,  is  placed  in  the  road,  and  then  is 
removed  at  the  public  expense. 

Italy.  VICTOR  CINQUE.  On  the  ordinary  roads  in 
Italy  a  permanent  staff  sweeps  the  snow  into  heaps  along 
the  sides  of  the  road  when  the  depth  does  not  exceed  1J^ 
inches  to  1J^  inches.  In  the  towns,  when  the  bed  of  snow 
is  relatively  thin,  the  snow  is  removed  by  flushing  it  with 
water  into  conduits  placed  expressly  for  this  purpose  along 
the  streets.  When  the  depth  of  the  snow  exceeds  2l/2  inches, 


180  HIGHWAY   ENGINEERING 

the  method  ordinarily  used  consists  of  sweeping  by  machines. 
The  machine  most  commonly  employed  for  the  removal  of 
snow  on  ordinary  roads  is  a  V-shaped  snow-plow  carrying  a 
weight  which  varies  with  the  depth  of  snow  to  be  removed. 
The  snow-plow  is  drawn  either  by  horses  or  by  oxen. 

As  regards  the  cost  of  removing  the  snow,  it  varies 
according  to  the  system  used.  In  certain  towns  as  soon  as 
the  total  surface  of  the  roadway  under  consideration  has 
been  determined,  the  price,  graduated  for  each  inch  of 
thickness  of  snow  for  sweeping  and  transportation  to  depots, 
is  determined  by  contract.  In  other  towns  a  special  price 
is  given  for  each  cubic  yard  of  snow  swept  and  heaped  along 
the  road  and  a  separate  price  for  the  transportation  to  the 
public  depot. 

On  ordinary  roads  used  by  tramways  a  snow-plow  is 
employed  on  that  part  of  the  road  used  by  ordinary  vehicles. 
Afterwards  the  removal  is  completed  by  sweepers  and  the 
road  at  its  most  important  points  is  entirely  freed  from  snow. 

Machines  which  have  been  designed  for  the  purpose  of 
thawing  the  snow  have  had,  as  yet,  no  appreciable  success, 
although  numerous  experiments  have  been  made. 

Norway.  J.  C.  ROSHAUW.  'At  Christiania  the  treat- 
ment of  snow  includes  not  only  its  removal  from  the  street, 
but  also  the  maintenance  and  repair  of  the  roads  used  by 
sledges.  The  work  consists  in  maintaining  the  roadways 
in  an  efficient  state  for  sledge  traffic  as  long  as  these  vehicles 
are  being  used  in  the  environs  of  the  town,  which  usually 
means  several  months  during  the  winter.  During  this 
time  only  the  paved  and  asphalted  footways  are  cleared 
of  ice  and  snow.  A  layer  of  snow  is  left  on  the  gravel  foot- 
ways and  is  sometimes  maintained  at  a  uniform  thickness 
by  means  of  snow-plows  or  scrapers.  The  snow  layer  is 


KEMOVAL   OF   SNOW   AND   ICE  181 

kept  about  6  inches  in  depth  except  in  the  gutters,  which 
are  kept  open.  In  the  spring  the  snow  is  broken  up  and 
carted  away,  as  is  also  the  excess  snow  during  the  winter. 
Sanding  is  employed  upon  the  roads  only  when  sledges  can- 
not be  used.  The  sidewalks,  however,  are  sanded  regularly. 

Russia.  PAUL  MIKHAILOFF.  The  severity  of  the 
climate  and  the  protracted  winter  in  Russia  are  such  that 
the  entire  removal  of  snow  is  never  attempted.  All  that  is 
done  is  to  level  the  coating  of  snow  in  the  street  and  so 
prepare  it  for  convenient  sleighing.  The  levelling  is  so  car- 
ried out  that  a  smooth  but  not  too  thick  bed  is  retained. 
Powdered  snow  which  is  heaped  up  by  the  snow-plow  or 
scraper  is  cleared  away  and  smoothed  down  by  a  snow- 
plow  drawn  by  four  or  eight  horses,  before  the  snow  has 
had  time  to  settle  or  to  become  hard  through  the  action  of 
the  traffic.  A  common  V-shaped  type  plow  is  used  which 
can  clear  a  layer  of  snow  6  inches  to  1  foot  deep  for  a  length 
of  9  to  12  miles  per  day.  The  inequalities  in  the  road 
surface  due  to  traffic  such  as  slopes,  ruts  and  pot  holes  cannot 
be  removed  by  the  plow  but  have  to  be  cleared  away  by 
manual  labor  with  picks  and  shovels.  For  this  same  pur- 
pose a  specially  designed  harrow  is  sometimes  used  which 
consists  of  a  triangular  platform  mounted  on  a  sledge  and 
capable  of  being  raised  or  lowered  by  suitably  arranged 
screws.  Steel  teeth  are  fixed  to  the  sides  of  the  platform 
which  cut  out  the  humps  of  snow  as  the  harrow  is  drawn 
along.  Consequently  the  height  of  the  platform  must  be 
adjusted  to  the  height  of  these  humps. 

In  some  cases  where  large  drifts  have  formed,  it  is  im- 
possible to  clear  them  away  even  by  hand  until  after  the 
snow  has  ceased  falling  and  hence  traffic  is  sometimes 
stopped  for  a  while.  The  direction  in  which  the  road  runs, 


182  HIGHWAY   ENGINEERING 

the  direction  in  which  the  wind  blows,  whether  or  not  the 
road  is  in  a  cut  or  on  an  embankment,  the  depth  of  the 
cuts  and  embankments  are  all  factors  which  influence  the 
method  of  operation.  At  such  places  on  the  road  where 
deep  layers  of  snow  are  formed,  snow  fences  should  be 
erected.  On  roads  fir  branches  are  employed  as  a  substitute 
for  the  specially  constructed  and  expensive  snow  fences. 
With  the  first  snowfall  at  the  beginning  of  winter  the  snow 
is  heaped  up  into  mounds  wherever  protection  is  needed. 
These  mounds  are  about  6  feet  in  width  and  are  placed  at  a 
distance  of  about  60  to  90  feet  from  the  road.  On  top  of 
these  mounds  are  fixed  branches  of  fir  trees,  about  3  to  6 
feet  high,  so  as  to  form  a  continuous  screen.  When  the  snow 
gets  over  the  top  of  these  branches  they  are  drawn  out  of 
the  snow,  other  mounds  are  raised  with  the  snow  itself  and 
the  branches  are  again  fixed  on  the  top.  This  operation  is 
repeated  as  many  times  during  the  winter  as  may  be  found 
necessary. 


CHAPTER  XVIII 

ROAD   SIGNS 

BRADACZEK,  THEODOR,  Imperial  Commissioner  of  Public 
Works,  Prague,  Austria. 

COLARD,  H.,  Delegate  of  the  Touring  Club  of  Belgium, 
Brussels,  Belgium. 

CHAIX,  EDMOND,  President,  Touring  Committee,  Auto- 
mobile Club  of  France,  Paris,  France. 

FOURMANOIS,  A.,  Delegate  of  the  Touring  Club  of  Belgium, 
Brussels,  Belgium. 

NAVAZZA,  AUGUSTE,  Director,  Touring  Club  of  Switzer- 
land, Geneva,  Switzerland. 

NEMETHY,  JOSEF,  Royal  Chief  Engineer,  Zilah,  Hungary. 

Pos,  G.  A.,  V ice-President,  Touring  Club  of  Netherlands, 
Baarn,  Netherlands. 

TOLLER,  GINO,  Engineer,  Milan,  Italy. 

VAN  MEERBEECK,  H.,  Delegate  of  the  Touring  Club  of 
Belgium,  Brussels,  Belgium. 

VAN  ZEEBROECK,  ED.,  Delegate  of  the  Touring  Club  of 
Belgium,  Brussels,  Belgium. 

Austria.  THEODOR  BRADACZEK.  The  road  signs  erect- 
ed at  each  cross  road  in  the  Kingdom  of  Bohemia  are  very 
substantial  and  give  very  complete  information  in  regard 
to  the  distance  and  the  direction  to  take.  These  sign  posts 

183 


184  HIGHWAY   ENGINEERING 

are  constructed  on  the  spot  either  of  stone  or  of  concrete. 
The  post  is  square  in  shape  and  about  5  feet  in  height.  On 
each  face  near  the  top  and  parallel  to  the  road  in  question 
are  given  the  names  and  the  distances  with  arrow  pointers 
to  the  terminal  cities  which  the  road  connects  and  below 
are  given  the  names  and  distances  to  the  intermediate  towns 
which  must  be  passed  through.  As  a  further  aid  to  the 
traveller  a  color  scheme  has  been  adopted  by  which  direc- 
tions are  indicated  by  colors.  For  instance,  roads  run- 
ning from  east  to  west  are  marked  in  red  or  brown  colors, 
those  from  north  to  south  in  blue,  those  from  northwest  to 
southeast  in  green  or  violet,  and  those  from  northeast  to 
southwest  in  yellow.  On  the  faces  of  the  monuments  above 
described  a  small  rectangle  of  the  appropriate  color  is  painted. 
This  same  color  scheme  is  further  carried  out  in  marking  the 
milestones  on  the  road  with  the  result  that  it  is  very  easy 
for  a  stranger  to  find  his  way.  The  writer  recommends  that 
the  road  maps  have  the  roads  to  different  points  shown  in 
colors  that  correspond  to  those  placed  on  the  milestones 
and  road  sign  posts. 

Belgium.  ED.  VAN  ZEEBROECK,  H.  COLARD,  A. 
FOURMANOIS  and  H.  VAN  MEERBEECK.  It  is  believed  that 
the  desired  warning  for  all  dangerous  points  can  be  given 
by  means  of  one  sign  bearing  for  a  symbol,  for  instance,  a 
triangle  to  mean  reduced  speed.  Such  a  sign  would  concern 
everybody  and  obedience  to  such  an  injunction  would  tend 
to  safeguard  all  people  on  the  road  against  dangers.  The 
use  of  a  number  of  signs,  which  indicate  the  specific  nature 
of  the  obstacle  and  which  are  recommended  in  the  interests 
of  motorists  alone,  tends  to  encourage  the  imprudence  of 
the  drivers  to  the  great  danger  of  those  they  pass  on  the 
road. 


ROAD   SIGNS  185 

France.  EDMOND  CHAIX.  The  General  Council  of 
the  Department  of  Roads  and  Bridges  has  declared  itself 
favorable  to  maintaining  those  signs  which  hava  been 
erected  under  the  auspices  of  the  Touring  Club. 

At  a  meeting  at  which  a  large  majority  of  the  auto- 
mobile clubs  of  the  continent  were  represented  it  was 
resolved  to  adopt  the  following  danger  signs  which,  with  the 
exception  of  the  third,  are  those  recommended  by  the  First 
Congress.  These  signs  are  four  in  number  and  indicate  the 
following  dangers  and  obstacles: 

1.  Turnings. 

2.  Obstacles  along  the  road  such  as  ditches,  humps, 
bridges,  etc. 

3.  Barriers,  road  crossings  or  railroad  crossings  when 
protected  by  barriers,  except  where  such  crossings  should  be 
classed  as  dangerous  crossings. 

4.  Dangerous    crossings,    road    crossings    or    railroad 
crossings  when  not  protected  by  barriers. 

It  was  thought  that  the  round  form  is  best  except  in 
places  where  railways  following  the  roads  have  a  similar 
shaped  sign  for  their  signals,  in  which  case  the  sign  should 
be  made  rectangular  in  order  to  avoid  confusion.  A  dia- 
meter of  about  27  inches  for  the  sign  was  adopted  and  the 
colors  chosen  were  white  for  the  inscription  and  dark  blue 
for  the  background.  It  was  felt  by  some  that  the  symbolic 
sign  is  sufficient  to  describe  the  danger,  but  others  thought 
that  the  sign  should  be  further "  supplemented  by  an  ex- 
planation of  the  danger  in  the  language  of  the  country  where 
the  sign  is  erected.  The  signs  are  placed  820  feet  in  front 
of  the  obstacle  to  be  pointed  out  and  on  the  side  of  the  road 
corresponding  to  the  direction  of  traffic. 

Hungary.     JOSEF  NEMETHY.     In  Hungary  the  dimen- 


186  HIGHWAY   ENGINEERING 

sions  and  inscriptions  of  the  kilometre  and  hectometre  stones 
have  been  fixed  by  the  government.  These  stones  are  of 
ashlar  and  are  marked  only  with  figures  indicating  distances. 
There  is  sufficient  room  to  mark  these  stones  with  all  the 
information  useful  to  the  tourist,  such  as  distances  to  differ- 
ent towns,  danger  signals,  etc.  The  writer  therefore  be- 
lieves that  the  following  system  might  well  be  adopted. 

The  kilometre  and  hectometre  stones,  which  serve  for 
the  marking  of  distances  along  the  roads,  should,  without 
waiting  for  an  international  agreement  relating  to  uniform 
signs,  be  altered  in  such  a  manner  as  to  give  the  directions 
and  distances  of  the  best  known  towns  which  lie  along  the 
route.  Danger  signals,  heights  above  sea  level  and  informa- 
tion with  respect  to  telegraph  and  telephone  stations  should 
also  be  inscribed  on  the  posts.  The  posts  should  be  painted 
white  and  have  their  inscriptions  marked  on  them  in  black, 
except  the  danger  signals,  which  should  be  given  in  red. 

Road  direction  signs  should  be  made  use  of  only  at 
branching  points,  road  crossings  and  at  the  beginnings  and 
ends  of  townships.  These  boards  could  be  attached  to 
posts  set  in  concrete  bases.  The  inscriptions  might  be 
printed  in  black  letters  on  a  white  or  on  a  light  blue  back- 
ground. 

Danger  boards  should  be  of  four  types  indicating  the 
following : 

1.  Turnings. 

2.  Obstacles  along  the  road  such  as  ditches. 

3.  Level  crossings. 

4.  Dangerous  crossings,  railroads,  etc. 

If  the  kilometre  stones,  however,  are  provided  with  the 
same  inscriptions  as  used  for  the  danger  boards,  the  latter 
are  more  or  less  superfluous  and  only  needed  in  places  where 


ROAD    SIGNS  187 

it  is  desirable  to  give  frequent  warnings  to  travellers  or 
where,  on  account  of  the  high  speed  of  the  motor  cars,  the 
legibility  of  the  inscriptions  could  not  be  depended  upon. 

Italy.  GINO  TOLLER.  The  Touring  Club  of  Italy  has 
had  a  regular  and  active  organization  for  the  erection  of 
road  signs  and  signals  since  1902.  Under  its  direction  about 
7,000  signs  of  different  kinds  have  been  erected  throughout 
Italy. 

The  signal  posts  of  the  Touring  Club  may  be  divided 
into  three  classes : 

1st.  Direction  signals,  or  sign  posts. 

2nd.  Danger  signals. 

3rd.  Special  signals. 

Every  signal  is  made  up  of  an  iron  pillar  painted  in  the 
national  colors  and  of  a  plate  on  which  is  given  information 
of  value  to  the  travelling  public.  The  plate  can  be  fixed 
to  walls,  etc.,  should  the  occasion  arise.  The  plate  is  rec- 
tangular and  of  varnished  iron,  the  sign  and  inscriptions 
being  in  white  on  a  dark  blue  ground.  On  every  post  are 
the  words  "  Touring  Club  Italiano"  and  a  number  for 
identification. 

Netherlands.  G.  A.  Pos.  Since  the  meeting  held  on 
December  1st,  1908,  both  the  Automobile  Club  and  the 
Dutch  Touring  Club,  although  in  favor  of  a  single  sign  post, 
have  placed  in  position  a  great  number  of  posts  bearing  the 
signals  adopted  by  the  First  Congress. 

At  crossings  of  light  railways,  which  are  laid  down  on 
their  own  right  of  way,  " level  crossing"  signs  are  put  up. 
For  tramway  crossings  where  the  track,  as  often  happens  in 
Holland,  crosses  from  one  side  to  the  other  of  the  road,  the 
"dangerous  crossing"  sign  is  used.  The  writer  believes 
that  the  signals  for  turns,  dangerous  crossings,  and  obstacles 


188  HIGHWAY   ENGINEERING 

along  the  road  are  satisfactory  in  the  majority  of  cases  as 
regards  traffic  requirements;  that  the  level  crossing  signal 
is  suitable  for  main  line  crossings  but  neither  this  sign  nor 
the  one  for  dangerous  crossings  is  adapted  for  warnings  at 
the  crossings  of  light  railways  or  suburban  lines;  that  the 
absence  of  any  warning  signal  at  descents  is  to  be  regretted. 
Switzerland.  AUGUSTE  NAVAZZA.  In  Switzerland  we 
were  forced  to  take  into  account  the  necessity  of  having 
conventional  signs  due  to  the  development  of  the  foreign 
motor  car  traffic.  In  1909  nearly  7,000  foreign  motor  cars 
entered  Switzerland  under  a  temporary  permit  for  the 
purpose  of  touring  the  country.  Under  such  conditions  the 
writer  believes  it  is  much  better  to  use  a  single  sign  to 
signify  " slacken  speed"  as  a  warning  for  all  points  of  danger 
no  matter  what  their  character  may  be.  Such  signals 
should  be  placed  within  600  to  750  feet  of  the  points  of 
danger. 


CHAPTER  XIX 

PIPE  SYSTEMS  IN  ROADS  AND  STREETS 

DE  HEEM,  PAUL,  Engineer  of  Bridges  and  Roads, 
Antwerp,  Belgium. 

HENTRICH,  HUBERT,  Commissioner  of  Public  Works, 
Crefeld,  Germany. 

Jlsz,  DIDIER,  Technical  Councilor,  Budapest,  Hungary. 

LEMEUNIER,  RICHARD,  Chief  Engineer  of  Bridges  and 
Roads,  Antwerp,  Belgium. 

LIDY,  GEORGES,  Chief  Engineer  of  Bridges  and  Roads, 
Bordeaux,  France. 

MmlLYFi,  JOSEPH,  Technical  Councilor.  Budapest, 
Hungary. 

PETERS,  FRITZ,  Commissioner  of  Public  Works,  Magde- 
burg, Germany. 

SILCOCK,  EDWARD  JOHN,  Past  President  of  the  Society  of 
Engineers,  Westminster,  London,  England,  Great  Britain. 

STEUERNAGEL,  KARL,  Commissioner  of  Public  Works, 
Cologne,  Germany. 

TUR,  PAUL,  Chief  Engineer  of  Bridges  and  Roads,  Paris, 
France. 

VON  MONTIGNY,  Commissioner  of  Public  Works,  Aix- 
la-Chapelle,  Germany. 

VON  SCHOLTZ,  A.,  Commissioner  of  Public  Works, 
Breslau,  Germany. 

•    189 


190  HIGHWAY   ENGINEERING 

Belgium.  RICHARD  LEMEUNIER  and  PAUL  DE  HEEM. 
A  commission  on  which  are  representatives  from  the  various 
departments  in  charge  of  the  roads,  sewers,  water-supply, 
gas,  lighting,  telephone  and  the  tramway  companies  could 
group  together  as  far  as  practicable  the  various  works  to  be 
carried  out  by  these  companies  and  so  minimize  the  number 
of  disturbances  to  the  road.  To  make  such  a  scheme 
successful  the  work  should  be  planned  so  that  all  of  the 
different  operations  will  be  finished  at  about  the  same  time. 

From  a  study  of  existing  conditions  in  the  city  of 
Antwerp,  it  was  concluded  that  pipe  galleries  could  not  be 
generally  adopted. 

In  the  city  of  Brussels  in  1908  a  subway  was  con- 
structed as  an  experiment  for  the  water  pipes  and  the 
electric  cables.  The  gas  pipes  were  purposely  excluded  be- 
cause of  the  danger  of  the  gas  main  and  the  electric  cables 
being  in  the  same  gallery.  The  subways  were  built  of  rein- 
forced concrete  and  cost  about  $4.12  per  linear  foot.  The 
experiment  is  of  such  recent  date  that  one  is  not  yet  entitled 
to  express  an  opinion  concerning  it. 

The  solution  which  seems  to  offer  the  most  advantages 
or  at  least  to  offer  the  fewest  objections  is  to  have  separate 
gas  and  water  pipe  lines  and  cables  on  both  sides  in  every 
street  and  to  place  them  under  the  sidewalks  wherever 
possible.  The  arrangement  of  the  pipe  lines  used  in  one 
of  the  streets  of  Antwerp  is  as  follows:  water  main,  1.6 
feet  in  from  the  curb;  gas  main,  4  feet;  cables,  5.6  feet. 
The  depths  at  which  the  different  pipes  are  laid  are  3.3 
feet,  2.6  feet,  and  2  feet  respectively. 

France.  GEORGES  LIDY.  It  is  evident  that  by  reason 
of  their  variety,  works  connected  with  reopening  roads  and 
streets  cannot  be  subjected  to  detailed  and  unchangeable 


PIPE    SYSTEMS   IN   ROADS   AND    STREETS  191 

rules.  Too  great  a  subdivision  of  services  or  departments 
connected  with  roads  may  lead  to  unnecessary  work  prej- 
udicial to  the  constant  maintenance  of  a  good  road  surface. 
It  is  also  necessary  that  all  the  departments  should  be  in 
constant  touch  with  one  another  and  that  their  individual 
work  be  constantly  subordinated  to  some  understanding 
whereby  the  unavoidable  obstruction  caused  by  their  works 
may  be  reduced  to  a  minimum.  The  disturbances  to  the 
road  cannot  be  overcome  in  urgent  and  unforeseen  cases, 
but  attempts  should  be  made  to  minimize  them  as  much  as 
possible.  As  to  works  which  can  be  carried  out  ad  libitum, 
it  is  recommended  that  they  should  not  be  commenced  until 
a  program  has  been  carefully  decided  upon  by  which  the 
various  works  may  be  carried  out  in  turn  with  as  little  in- 
terference as  possible  with  public  convenience  and  traffic. 

The  sewer  is  usually  located  in  the  middle  of  the  street. 
In  the  older  sewers  and  in  the  newer  ones  that  are  too  small 
to  be  entered,  the  manholes  are  placed  in  the  roadway. 
For  the  larger  sewers  the  tendency  now  is  to  place  manholes 
in  the  sidewalks,  connecting  them  to  the  sewers  by  a  branch. 
Gas  pipes  are  generally  placed  under  the  carriageway,  since 
they  are  not  allowed  in  the  sewers  from  the  standpoint  of 
danger.  The  light  cables  are  almost  invariably  placed 
under  the  sidewalks,  and  at  road  crossings  pipes  or  conduits 
are  often  made  obligatory  so  that  the  cable  can  be  with- 
drawn without  disturbing  the  road.  As  a  general  rule  there 
is  only  one  water  main  in  each  street  and  it  is  placed  under 
the  carriageway.  It  is  only  in  the  great  cities  and  in  some 
of  the  main  thoroughfares  that  water  pipes  are  found  under 
each  sidewalk. 

It  is  desirable  to  place  under  the  sidewalks  all  of  the 
conduits  such  as  those  for  gas,  electricity  and  water.  Where 


192  HIGHWAY   ENGINEERING 

water  pipes,  etc.,  must  be  necessarily  placed  under  the 
carriageway,  the  number  of  fixtures  should  be  diminished 
as  much  as  possible  and  those  should  be  selected  which  are 
most  permanent. 

There  does  not  seem  to  be  any  advantage  in  shifting 
a  single  main  from  the  carriageway  to  the  sidewalk.  The 
presence  of  a  main  under  the  carriageway  is  not  objectionable 
except  in  so  far  as  the  repairs  and  alterations  to  the  house 
connections  are  concerned.  The  use  of  two  mains  one  on 
either  side  of  the  street  is  of  great  advantage,  since  the 
house  connections  are  quite  short  and  do  not  interfere  with 
the  carriageway.  In  old  roads  where  a  single  main  exists, 
the  construction  of  duplicate  mains,  one  on  either  side  of 
the  street,  could  be  substituted  for  the  old  main  when 
extensive  repairs  were  being  made. 

If  gas  pipes  are  well  laid  with  proper  joints,  there  would 
be  no  danger  from  placing  them  in  well  ventilated  galleries. 

France.  PAUL  TUR.  The  experience  in  Paris  is  that 
well  ventilated  subways  can  safely  contain  gas  pipes.  Un- 
fortunately subways  are  seldom  aerated  as  such  ventilation 
is  very  difficult  to  carry  out.  The  supervision  and  inspec- 
tion of  such  services  in  subways  cannot  be  compared  to  that 
in  dwelling  houses,  in  consequence  of  which  fact  danger 
from  escapes  of  gas  are  very  serious. 

Germany.  FRITZ  PETERS,  KARL  STEUERNAGEL,  A. 
VON  SCHOLTZ,  VON  MONTIGNY,  HUBERT  HENTRICH.  In 
Dresden  model  arrangements  have  been  made  with  respect 
to  road  engineering  operations  which  involve  the  construc- 
tion of  gas  mains,  water  mains,  etc.,  so  that  they  may  be 
regulated  for  a  whole  year  ahead  and  in  such  manner  that 
all  the  administrative  departments  concerned  may  lay  their 
plans  accordingly,  and  that  the  greatest  possible  considera- 


PIPE    SYSTEMS   IN   ROADS   AND    STREETS  193 

tion  may  be  given  to  the  interests  of  the  adjacent  owners 
and  traffic. 

In  Berlin  the  arrangement  of  the  mains  is  as  follows. 
A  similar  arrangement  is  used  in  Breslau. 

1.  The  pipe  systems  are  placed  in  the  footway  only 
when  the  breadth  of  the  latter  exceeds  16.4  feet,  otherwise 
in  the  carriageway. 

2.  The  gas  mams  ranging  up  to  15  inches  in  diameter 
are  placed  under  the  footway;   when  larger  than  this  they 
are  placed  in  the  carriageway. 

3.  Water  mains  up  to  9  inches  in  diameter  are  laid  in 
the  footways  when  'these  have  a  width  of  8  feet  or  more; 
when  of  greater  diameter  than  this,  or  when  the  footways 
are  narrower,  they  are  placed  in  the  carriageway. 

4.  The  electric  cables,  with  the  distance  telegraph  and 
telephone  cables  are  placed  close  to  the  line  of  the  buildings, 
a  strip  of  about  3J/2  feet  to  5  feet  in  width  being  reserved 
for  them. 

The  tramway  cable  is  laid  next  to  the  curbstone,  while 
an  intermediate  position  between  the  gas  and  water  mains 
or  drainage  pipes  is  allotted  to  the  lighting  cables. 

With  this  arrangement  the  footway  ground  is  utilized 
to  the  utmost,  so  much  so  that,  even  with  a  width  of  foot- 
way of  16.4  feet,  there  is  no  room  left  for  the  planting  of  trees. 

For  suburban  roads,  sewers  and  drains  may  be  placed 
under  the  carriageway,  since  there  is  little  likelihood  of 
the  system  being  disturbed  if  properly  constructed  in  the 
first  place.  It  is  believed  that  there  are  advantages  to 
laying  the  water  main  under  the  carriageway,  as  this  would 
guarantee  against  the  washing  out  of  the  building  founda- 
tions, which  might  occur  in  case  of  a  break  if  the  main  were 
under  the  footway.  This  arrangement  would  also  prevent 


194  HIGHWAY   ENGINEERING 

any  disturbance  from  a  similar  cause  to  the  other  services 
which  may  well  be  placed  under  the  footway.  A  similar 
position  is  recommended  for  the  gas  main,  as  there  is  more 
or  less  leakage  which  might  be  dangerous  to  the  occupants 
of  the  buildings  if  laid  close  to  the  building  line,  as  well  as 
injurious  to  trees.  The  use  of  two  mains  for  each  service, 
one  on  each  side  of  the  road,  is  an  advantage  as  far  as  the 
disturbance  to  traffic  is  concerned,  and  is  the  most  con- 
venient for  making  connections.  It  can  only  be  an  advan- 
tage from  a  financial  point  of  view,  however,  when  the^  cost 
of  the  branches  from  the  main  to  the  buildings  on  either 
side  is  greater  than  the  cost  of  the  two  mains.  Telegraph 
and  telephone  cables  might  also  be  placed  in  iron  pipes  or 
conduits  under  the  carriageway,  as  there  is  slight  chance  of 
their  being  disturbed. 

In  place  of  the  usual  form  of  concrete  foundations  for 
pavements,  the  use  of  concrete  prisms  made  of  1 : 3 : 5  mixture, 
of  a  height  of  7  inches,  a  breadth  of  10  inches,  and  a  length  of 
12  inches  laid  on  the  properly  constructed  road  surface  has 
proved  eminently  satisfactory.  The  prisms,  which  are 
set  with  open  joints  in  coarse  sand,  can  at  any  point  be  at 
once  picked  out,  and,  on  the  completion  of  repairs  to  a  line 
of  piping,  etc.,  can  be  put  in  again. 

Great  Britain.  EDWARD  JOHN  SILCOCK.  The  cost  of 
sewers,  large  water  mains  and  other  similar  works  is  very 
considerable  and,  having  regard  to  the  saving  of  interest 
on  and  the  repayment  of  capital  expenses,  it  is  often  more 
economical  to  defer  the  construction  of  the  works  until  they 
are  actually  required  than  to  execute  them  prematurely  to 
suit  the  road  making  program. 

No  doubt  in  an  ideal  state  there  would  be  no  such  thing 
as  dual  control  and  the  various  branches  of  the  public 


PIPE    SYSTEMS   IN   ROADS   AND    STREETS  195 

service  would  be  under  one  supreme  head,  but  under  present 
conditions  this  ideal  is  never  attained. 

The  use  of  subways  would  only  partially  prevent  the 
disturbance,  of  the  roads,  since  where  subways  are  con- 
structed, it  is  usually  found  that  one  such  structure  must 
be  placed  in  the  center  of  the  road  from  which  the  branch 
drains  or  service  pipes  for  water,  gas,  etc.,  are  led  across  the 
road  to  the  houses.  This  involves  the  tearing  up  of  the 
road  every  time  a  new  service  is  required  or  an  old  one 
is  repaired.  The  other  alternative  is  to  construct  two 
subways,  one  on  each  side  of  the  road  under  the  footways, 
or,  in  cases  where  basements  extend  beyond  the  building 
line,  as  near  the  basement  wall  as  possible,  in  which  case 
the  service  pipe  would  be  carried  directly  through  the  walls 
of  basements  of  private  premises  without  the  necessity  of 
opening  up  the  surface  of  the  road.  The  chief  objection, 
however,  to  subways  is  the  financial  one  and  it  is  found  that 
except  in  the  very  busiest  and  most  important  streets  of 
large  towns  it  is  quite  impracticable  financially  to  construct 
a  system  of  subways. 

On  country  roads  it  is  desirable,  as  far  as  possible,  to 
select  the  grass  shoulders,  where  such  exist,  as  suitable 
places  for  pipe  trenches.  In  many  cases  where  there  are 
no  grass  shoulders  it  becomes  necessary  to  place  the  pipe 
trench  upon  the  metalled  portion  of  the  road.  Where  the 
roads  are  straight  and  wide,  there  is  usually  no  difficulty 
in  placing  the  pipe  on  the  haunch  so  that  it  shall  not  unduly 
interfere  with  traffic  during  construction  or  permanently 
through  the  presence  of  manhole  or  valve  covers.  Where 
sewers  have  to  be  constructed  in  winding  roads,  it  is  necessary 
to  lay  the  pipes  in  straight  lines,  which  involves  the  trench 
crossing  over  from  side  to  side  of  the  road  in  order  to 


196  HIGHWAY   ENGINEERING 

minimize  the  number  of  manholes  required.  In  dealing 
with  water  mains,  gas  mains  and  other  conduits  made  of 
iron  pipes,  it  is  generally  possible  to  adjust  the  joints  of  the 
pipes  so  that  the  trench  will  follow  the  line  of  the  road. 
For  electric  light  cables  laid  in  ordinary  roads,  especially 
hi  suburban  districts,  the  conduits  can  be  placed  with  ad- 
vantage under  the  footways  unless  the  latter  are  constructed 
with  concrete  or  asphalt,  surfaces  which  are  hard  to  repair 
in  the  event  of  their  being  disturbed. 

Hungary.  JOSEPH  MIHALYFI  and  DIDIER  JASZ.  In 
Budapest  each  of  the  footways  is  usually  one-fifth  of  the  total 
width  of  roadway  and  varies  in  other  instances  from  about  5 
feet  to  25  feet  in  width.  The  sewer  is  generally  placed  in  the 
middle  of  the  street.  On  streets  less  than  49  feet  in  width  the 
gas  main  is  placed  on  one  side  of  the  street  under  the  road- 
way, 3.3  feet  away  from  the  curb,  and  the  water  main  occu- 
pies a  similar  position  on  the  other  side  of  the  street.  The 
electric  light  and  telephone  cables  are  laid  under  the  side- 
walks as  near  the  houses  as  possible.  The  telephone  cables 
are  placed  in  concrete  block  conduits  which  contain  in  some 
cases  as  many  as  forty-eight  cables  and  are  placed  sufficiently 
deep  so  that  the  other  services  to  the  houses  can  pass  over 
them.  On  streets  of  a  greater  width  than  49  feet  there  is 
placed  both  a  water  main  and  a  gas  main  on  either  side  of 
the  road,  3.3  feet  and  6.6  feet  away  from  the  curb  respec- 
tively. On  streets  of  a  still  greater  width,  82.0  feet  and 
more,  on  each  side  of  the  road  the  pipes  are  placed  as  follows : 
a  water  main  at  the  curb,  then  the  secondary  street  sewers, 
and,  at  a  distance  of  about  10  feet  from  the  curb,  the  gas 
main.  Gas  mains  are  placed  under  the  road  at  a  depth  of 
from  3}/2  feet  to  5  feet.  Water  pipes  are  generally  laid  from 

feet  to  5  feet  below  the  surface  of  the  pavements. 


CHAPTER  XX 

TRAMWAYS  ON  ROADS  AND  STREETS 

BONNE  VIE,    AUGUSTS,    Chief   Engineer    of   Railroads, 
Brussels,  Belgium. 

GALLIOT,  FRANCOIS,  Chief  Engineer  of  Bridges  and  Roads, 
Dijon,  France. 

GELINCK,  W.  G.  C.,  Engineer  of  Waterways,  Assen, 
Netherlands. 

GERLACH,  FRIEDRICH,  Imperial  and  Municipal  Com- 
missioner  of  Public  Works,  Berlin,  Germany. 

SPITERI,  JOSE  RODRIGUEZ,  Chief  Engineer  of  Highways, 
Canals  and  Harbors,  Malaga,  Spain. 

TOLLER,  GINO,  Engineer,  Milan,  Italy. 

ULLMAN,    G.,    Chief  Engineer  of  Tramways,   Vienna, 
Austria. 

VAN  HEYST,  D.  A.,  Engineer  of  Waterways,  Ziitphen, 
Netherlands. 

VON   SZTROKAY,    STEFAN,    Chief  Engineer,   Budapest, 
Hungary. 

WALLAND,  C.  B.  J.,  Engineer  of  Public  Works,  The 
Hague,  Netherlands. 

WYNNE-ROBERTS,  R.  O.,  M.  Inst.  C.  E.,  F.  R.  San. 
Inst.,  Westminster,  London,  England,  Great  Britain. 

197 


198  HIGHWAY  ENGINEERING 

Austria.  G.  ULLMAN.  The  only  advantage  of  con- 
structing a  railway  on  the  road  is  the  saving  to  the  railway 
company  of  the  money  that  would  otherwise  have  to  be 
spent  for  a  right  of  way  and  a  probable  increased  cost  of 
construction.  The  disadvantages  both  from  the  standpoint 
of  the  railroad  company  and  of  those  who  have  charge  of 
the  upkeep  of  the  adjoining  road  are  many. 

Government  highways  may  be  used  for  light  lines 
without  compensation  having  to  be  given,  the  railway 
company  being  liable  for  all  expenses  accruing  from  the 
reconstruction  of  the  roadway  necessitated  by  the  installa- 
tion of  the  track  and  for  the  maintenance  and  cleansing 
of  that  part  of  the  road  actually  made  use  of  by  the  line. 
The  company  is  not  liable  for  the  costs  of  strengthening 
bridges  or  the  maintenance  and  cleansing  of  banks  and 
ditches  along  the  lines.  When  the  track  is  built  along  the 
side  of  the  road  it  may  be  separated  from  the  rest  of  the 
roadway  by  some  kind  of  barrier  but  only  when  it  is  done 
in  a  manner  which  will  permit  the  rapid  removal  of  the 
barriers  in  case  of  need.  The  rail  gauges  used  in  Austria 
are  2.49  feet,  3.28  feet  and  4.71  feet. 

Belgium.  AUGUSTE  BONNE  VIE.  In  Belgium,  outside 
the  built  up  districts,  the  track  is  usually  laid  on  one  side 
of  the  road  or  on  an  elevated  bank  inaccessible  to  ordinary 
traffic.  A  minimum  width  from  track  curb  to  the  center 
of  the  road  of  about  20  feet  on  a  rural  road  and  of  23  feet  on 
a  main  highway  is  required.  When  the  track  is  constructed 
along  the  roadside  the  surface  drainage  is  obtained  by 
laying  open  stone  drains  underneath  the  track  and  leading 
to  the  ditch.  The  rails  are  of  the  Phoenix  type  with  a 
groove  about  1J/2  inches  wide.  In  places  where  the  rails 
cross  a  metalled  road,  the  metalling  is  generally  replaced 


TRAMWAYS    ON   ROADS   AND    STREETS  199 

with  stone  block  pavements  over  a  suitable  area.  The 
rails  both  on  the  paved  portions  of  the  road  and  on  the 
roadsides  as  well  as  on  special  tracks  are  fixed  on  creosoted 
oak  sleepers. 

The  construction  of  railways  on  the  road  is  always 
disadvantageous  to  the  concession  holder  on  account  of 
the  reduced  speed  at  which  the  cars  have  to  be  operated 
and  the  increase  in  expense  of  track  maintenance.  On  the 
other  hand,  it  often  happens  that  the  interest  of  the  people 
to  be  served  is  better  accommodated  by  a  line  running  in 
the  roadway,  since  it  affords  easier  access  to  their  homes  or 
places  of  business.  The  only  advantage  which  the  use  of 
an  existing  road  for  a  track  may  offer  is  the  relief  of  main- 
tenance of  that  part  of  the  road  used  by  the  track.  Where 
a  track  is  constructed  on  a  paved  road,  especially  if  it  is  a 
double  track,  this  advantage  may  be  of  some  importance. 

When  the  track  is  built  in  a  metalled  road,  the  cost  of 
maintaining  the  road  is  increased.  The  rails  interfere  with 
good  construction. 

Statistics  show,  that  in  Belgium  at  least,  the  number  of 
accidents  caused  by  railways  being  built  on  the  roads  are 
very  few. 

From  the  reports  of  70  light  railway  companies  which 
sent  in  replies  to  the  list  of  questions  regarding  rail  tracks 
to  the  Tramway  and  Light  Railway  Congress  of  Munich, 
it  is  found  that  there  were  very  few  which  used  longitudi- 
nal concrete  supports  under  the  rails. 

France.  FRANgois  GALLIOT.  A  decree  was  issued  in 
France  in  1906  by  the  Ministry  of  Public  Works  prohibiting 
the  construction  of  tramways  on  roads  save  in  exceptional 
cases.  The  railway  company  is  obliged  to  maintain  the 
area  between  the  rails  and  an  area  1.61  feet  outside  each  rail. 


200  HIGHWAY   ENGINEERING 

Economy  in  construction  is  evidently  the  only  reason 
which  can  be  offered  in  favor  of  building  a  tramway  along- 
side the  road.  Taking  everything  into  consideration  one 
must  come  to  the  conclusion  that  in  hilly  countries  the 
location  of  tramways  alongside  the  public  roads  can  be 
recommended  only  in  extreme  cases.  One  is,  therefore,  led 
to  the  conclusion,  when  considering  nothing  else  but  the 
railway,  that  laying  it  alongside  the  road  may  be  compulsory 
in  mountainous  countries,  but  generally  speaking  it  will  be 
preferable  to  provide  an  independent  right  of  way  for  the 
tramway  in  countries  of  average  hilly  character. 

In  cases  where  it  is  necessary  to  lay  the  tramway  upon 
the  road,  if  the  track  is  so  placed  as  to  be  inaccessible  to 
the  road  vehicles,  its  deleterious  effect  upon  the  road  is 
reduced  to  a  minimum.  Under  these  conditions  all  impor- 
tant kinds  of  road  work,  such  as  resurfacing  and  repairing, 
can  be  carried  on  in  the  usual  manner  with  little  incon- 
venience. In  the  case  of  tracks  laid  along  the  road  that 
are  accessible  to  the  road  vehicles  the  use  of  ordinary 
methods  of  maintenance  is  either  very  difficult  or  even 
ineffectual.  Where  grooved  or  twin  rails  are  used,  resurfac- 
ing can  be  carried  out  between  the  rails  provided  it  is  done 
very  carefully,  but  where  the  other  types  of  rails  are  used 
it  becomes  very  difficult.  The  space  between  the  rails  in 
this  case  has  to  be  maintained  by  special  hand  labor  and  is 
a  source  of  continual  trouble  to  the  road  builder. 

Germany.  FRIEDRICH  GERLACH.  The  maintenance 
of  any  surface  adjacent  to  the  tram-rails  which  are  laid  in 
the  roadways  gives  more  trouble  and  is  more  costly  than  the 
same  road  surface  under  the  same  traffic  but  without  a 
track.  The  up  and  down  movement  of  the  rails  under 
traffic  is  very  injurious  to  the  adjoining  pavements,  hence 


TRAMWAYS   ON   ROADS   AND   STREETS  201 

the  importance  of  a  solid  bed  for  the  rails  must  not  be 
overlooked.  In  the  case  of  some  pavements  the  rails  may 
be  laid  on  ties  bedded  in  good  gravel  without  any  material 
damage  resulting.  Asphalt  and  wood  block  paving,  how- 
ever, are  susceptible  to  a  very  small  movement  of  the  rail 
both  laterally  and  vertically,  and  hence  the  most  rigid 
bed  is  none  too  good.  With  the  increase  in  the  weight  of 
the  rolling  stock  and  the  introduction  of  electric  traction, 
the  rail  sections  and  the  track  construction  have  had  to  be 
changed  in  order  to  stand  up  under  the  traffic.  One  of 
the  principal  objections  to  the  usual  method  of  concrete 
foundations  for  the  rails  is  that  the  track  cannot  be  used 
until  the  concrete  sets  up,  thus  sometimes  causing  expensive 
delays.  To  overcome  this  objection  and  to  provide  a  founda- 
tion that  can  be  rapidly  constructed  the  Reinhardt  method 
of  construction  was  developed  in  Germany.  A  description 
of  the  latest  improved  form  is  here  given.  It  consists  essen- 
tially of  rectangular  shaped  reinforced  concrete  blocks  about 
5  inches  thick,  31  inches  long  and  20  inches  broad.  The  block 
is  so  molded  that  in  the  top  surface  a  trough  is  provided  which 
is  wide  and  deep  enough  so  that  when  the  rail  is  set  in  it 
the  head  of  the  rail  will  be  flush  with  the  surface  of  the 
block.  Bolts  are  provided  in  each  block  so  that  rail  fasten- 
ings may  be  put  in  and  be  attached  to  the  rail  base.  The 
whole  block  is  thoroughly  reinforced  and  the  reinforcing 
rods  are  allowed  to  project  beyond  the  faces  of  the  blocks 
which  are  parallel  to  the  rail  so  as  to  bond  with  the  concrete 
that  is  later  put  in  between  the  rails.  The  blocks  are 
placed  in  the  bottom  of  the  trench  in  which  the  rails  are  to 
rest  and  are  first  covered  with  a  viscous  asphalt.  They  are 
then  pushed  under  the  rails  which  have  been  jacked  up  to 
receive  them  and  the  rails  are  then  screwed  down  to  the 


202  HIGHWAY   ENGINEERING 

fastenings.  The  space  between  the  bottom  of  the  blocks 
and  the  earth  roadbed  is  then  carefully  filled  with  a  dry 
mixture  of  concrete  which  is  carefully  tamped.  After  a 
fairly  long  section  is  completed  in  this  manner,  the  bolt 
holes  are  run  in  with  liquid  cement  and  the  space  left  be- 
tween the  rails  and  the  side  walls  of  the  reinforced  con- 
crete troughs  is  filled  with  asphalt.  The  space  then  left 
between  the  faces  of  the  blocks  between  the  rails  is  filled 
with  well  rammed  concrete.  These  reinforced  concrete 
blocks  are  laid  close  enough  together  so  that  the  joints 
between  their  ends  are  practically  closed  up  by  pouring 
them  with  cement  mortar.  Cross  ties  are  done  away 
with.  In  this  construction  the  rails  do  not  come  in  con- 
tact with  the  concrete  at  all,  but,  on  the  contrary,  are  sep- 
arated from  it  by  the  lateral  projections  of  the  reinforced 
concrete  blocks  and  from  these  again  by  asphalt.  In  cases 
of  renewal  the  asphalt  can  be  readily  removed  by  means 
of  heat,  and  after  the  nuts  are  unscrewed  from  the  fastenings, 
the  rails  can  be  easily  lifted  out. 

Great  Britain.  R.  O.  WYNNE-ROBERTS.  Light  rail- 
ways on  British  roads  must  have  one  row  of  granite  blocks 
or  other  suitable  material  having  an  average  width  of  6 
inches  on  each  side  of  the  rails  and,  if  laid  on  the  waste 
land  along  a  road,  provision  must  be  made  for  the  drainage 
of  the  road. 

In  almost  all  of  the  populous  centers  in  Great  Britain 
tramways  have  been  laid  on  public  streets  and  roads.  The 
foundations  for  these  tramways  are  generally  constructed 
of  Portland  cement  concrete.  Although  in  some  cases  a 
tramway  has  been  laid  on  one  side  of  the  road,  the  general 
practice  is  to  lay  the  rails  in  or  near  the  center.  Stone 
block  and  wood  block  pavements  have  been  used  for 


TRAMWAYS    ON   ROADS    AND    STREETS  203 

construction  between  and  outside  of  the  rails.  When  the 
rails  are  laid  in  the  center  of  the  road  the  traffic  is,  in  pro- 
portion to  the  frequency  of  the  service,  prevented  from 
using  the  best  portion,  namely  the  crown  of  the  road,  and 
also  from  passing  from  one  side  to  the  other.  On  the  other 
hand  when  the  tramway  cars  pass  at  more  or  less  prolonged 
intervals  the  vehicular  traffic  tends  to  follow  the  rails  and 
causes  tracking  on  the  marginal  pavements. 

Hungary.  STEFAN  VON  SZTROKAY.  Although  no  law 
exists,  the  light  railways  outside  of  the  large  towns  are  laid 
on  permanent  ways  of  their  own  outside  of  the  road  limits. 

The  tramways  in  Hungary  generally  use  the  grooved 
rail.  The  stepped  rail  so  common  in  America  is  not  used 
at  all.  There  are  some  instances,  however,  on  roads  with 
a  light  traffic  where  the  ordinary  T  rail  section  is  used  and 
the  groove  is  nothing  more  than  a  furrow  next  to  the  rail- 
head cut  out  of  the  adjoining  pavement.  In  order  to  obtain 
this  arrangement  the  macadam  pavement  is  first  completely 
finished  without  any  regard  being  paid  to  the  track  and 
then  the  groove  is  cut  out  with  a  pickaxe.  The  ordinary 
grooved  rail  section  which  is  rolled  at  the  mills  is  not  used 
very  often  in  Hungary.  The  fixed  groove  can  not  be  widened 
out  where  curves  occur  and  hence  the  groove  is  generally 
wider  on  the  straight  stretches  than  is  absolutely  necessary, 
thus  being  unfavorable  for  the  ordinary  road  vehicle  traffic. 
The  objections  just  cited  may  be  done  away  with  and  a 
grooved  rail  may  be  obtained  by  the  use  of  the  Haarman 
twin  rail  which  is  used  in  Budapest.  This  system  consists 
essentially  of  two  bearing  rails  which  are  of  equal  height 
and  width,  both  having  a  stepped  head.  Each  rail  of  the 
track  is  made  up  of  two  of  these  rails  laid  so  that  the  stepped 
heads  form  a  groove.  A  special  form  of  flange  is  used  on 


204  HIGHWAY   ENGINEERING 

the  wheel  wherein  the  projection  on  the  flange  lies  in  the 
middle  of  the  tread  with  the  result  that  two  treads  bear  on 
each  rail.  The  joints  are  bolted  together  by  means  of  a 
fishplate  which  lies  between  the  two  rails.  By  laying  the 
rails  so  that  the  joint  for  one  rail  comes  opposite  the  middle 
of  a  rail  length  of  the  other  rail  only  one-half  of  the  whole 
section  is  interrupted  at  each  joint.  The  result  is  that  the 
strength  at  the  joint  is  10  to  15  per  cent  greater  than  the 
section  of  the  twin  rail.  This  is  the  only  system,  so  far  as 
the  writer  is  aware,  where  a  double  bearing  surface  is  pro- 
vided. 

Italy.  GINO  TOLLER.  Light  railways  may  be  con- 
structed on  the  public  highways  provided  a  clear  width  of 
about  13  feet,  measured  from  the  outside  of  the  cars,  is  left 
for  the  vehicle  traffic.  On  bridges  and  for  short  lengths 
through  built  up  districts  and  in  the  case  of  special  obstacles, 
a  smaller  clear  width  is  allowed. 

In  Italy  there  are  2,497  miles  of  tramways,  2,217  miles 
of  which  are  built  with  Vignole  rails  and  280  miles  with 
Phoenix  and  Hart  wick  rails.  A  majority  of  Italian  tram- 
ways, 61  per  cent,  make  use  of  the  Provincial  Roads,  25 
per  cent  of  them  use  the  Communal  Roads,  and  9}/2  per  cent 
have  special  ways  of  their  own.  As  to  the  systems  of 
traction,  about  81  per  cent  are  steam  and  19  per  cent  are 
electric,  but  nearly  all  the  recent  lines  are  electric. 

Where  the  Vignole  rail  is  used  it  is  impossible  to  use 
any  form  of  metalling  between  the  rails.  The  tramways 
are  placed  generally  at  one  side  of  the  road  and  the  surface 
occupied  is  shut  off  from  the  ordinary  carriageway. 

The  additional  maintenance  expenses  on  a  road  where 
a  tramway  exists  are  not  easy  to  estimate.  As  a  result  of 
an  inquiry  made  by  the  writer,  in  several  provinces  it  was 


TRAMWAYS   ON   ROADS   AND    STREETS  205 

found  that  the  increase  varied  from  5  per  cent  to  20  per 
cent  and  even  then  the  road  surfaces  were  never  in  very 
good  condition. 

Netherlands.  W.  G.  C.  GELINCK  and  D.  A.  VAN 
HEYST.  Sanction  is  given  to  the  construction  of  a  tramway 
on  a  National  Highway  only  under  a  series  of  conditions  or 
regulations  drawn  up  according  to  a  standard  form.  Some 
of  the  more  important  stipulations  are  the  following: 

1.  In   designing   the   tramway   the   greatest   possible 
width  must  be  left  for  the  ordinary  road  traffic.     The 
track  must  be  so  laid  that  the  road  drainage  is  not  inter- 
fered with. 

2.  Where  the  track  is  laid  on  a  paved  road,  the  cross 
sleepers  must  be  so  placed  that  their  upper  surfaces  are  at 
least  2  inches  below  the  lower  surface  of  the  paving.     Where 
the  track  passes  over  a  masonry  bridge,  the  thickness  of  the 
layer  of  ballast  between  the  extrados  of  the  arch  and  the 
under  side  of  the  sleepers  must  be  at  least  10  inches. 

3.  At  crossings  the  railway  company  must  lay  down 
paving  that  will  not  interfere  seriously  with  either  the 
drainage  or  the  ordinary  traffic.     The  longitudinal  slope 
of  the  road  must  not  be  steeper  than  1  in  100. 

4.  Double  lines  are  to  keep  to  the  same  side  of  the 
road  as  the  main  line  and  shall  be  so  constructed  as  not  to 
encroach  on  the  carriageway. 

5.  Where  the  rails  are  flush  with  the  surface  of  the 
road  they  must  be  grooved  or  be  provided  with  guard  rails, 
say,  of  flat  plates  on  tangents  and  of  regular  guard  rails  on 
curves. 

The  gauges  of  the  tracks  in  the  Netherlands  are  2.46 
feet,  3.28  feet,  3.5  feet  and  4.71  feet.  The  rails  are  generally 
of  the  Vignole  type  fixed  to  cross  ties.  Where  the  rails  are 


206  HIGHWAY   ENGINEERING 

laid  flush  or  sunk  in  the  road  surface,  supports  are  fastened 
between  the  foot  of  the  rails  and  the  sleepers.  On  most  of 
the  tramways  where  cross  tie  construction  is  preferred  to  the 
longitudinal  supports,  the  ties  are  bedded  in  ballast  almost 
always  composed  of  sand  which  gives  rise  to  much  dust. 

Netherlands.  C.  B.  J.  WALLAND.  The  subsoil  of 
The  Hague  consists  nearly  everywhere  of  firm  and  sandy 
ground.  In  the  older  parts  of  the  city  this  subsoil  has 
acquired,  in  consequence  of  the  traffic,  a  greater  density 
than  in  the  more  recently  developed  quarters.  On  streets 
paved  with  stone  block  or  brick,  the  subsoil  was  deemed  to 
be  sufficiently  compact  to  allow  the  rails  to  be  laid  on  the 
sandy  substratum  without  taking  special  precautions, 
since  it  was  thought  that  during  the  first  few  years  the  work 
of  constantly  raising  the  rails  to  the  desired  level  would 
be  cheaper  than  the  extra  cost  of  building  a  solid  foundation, 
and  experience  has  substantiated  this  opinion.  The  Phoe- 
nix grooved  rail  was  chosen  as  the  appropriate  rail  section. 
Although  this  method  of  construction  was  satisfactory 
where  stone  block  or  brick  pavements  were  used  in  the 
adjoining  road  surface,  it  was  not  successful  for  the  track 
construction  where  the  rails  had  to  be  laid  in  an  asphalt 
pavement. 

In  this  latter  case  a  solid  bed  of  concrete  was  placed 
in  the  track  trench.  After  this  bed  had  sufficiently  set 
up,  the  rails  were  laid  on  it  and  brought  to  the  correct 
level  by  means  of  wooden  wedges  placed  at  intervals  of 
about  6  feet  in  such  a  manner  that  the  distance  between  the 
surface  of  the  concrete  bed  and  the  rail  base  was  about  1J4 
inches.  Then  the  footing  of  the  rail  was  surrounded  with 
a  bed  of  poured  asphalt.  Along  the  rails  on  either  side 
hard  Australian  wood  blocks  were  laid.  This  form  of  con- 


TRAMWAYS    ON   ROADS   AND    STREETS  207 

struction  did  not  work  out  particularly  well  because  it 
allowed  a  vertical  movement  of  the  rail,  which  disturbed 
the  wood  blocks,  permitting  water  to  trickle  in.  It  was 
found  on  making  an  examination  that  the  asphalt  no  longer 
completely  adhered  around  the  rail,  although  the  wooden 
wedges  on  which  the  track  had  been  laid  were  in  good 
condition.  It  was  also  observed  that  the  movements  of  the 
rail  first  commenced  at  the  rail  joints. 

To  remedy  these  objections  the  method  of  construction 
has  been  modified.  Asphalt  is  no  longer  poured  under  the 
rails  and  the  latter  are  placed  on  oak  sleepers  having  a 
width  equal  to  the  base  of  the  rail  and  a  thickness  of  about 
lj/2  inches.  The  sleepers  are  firmly  fixed  to  the  rails  after 
the  rails  have  been  brought  to  the  desired  level.  The  bed 
of  concrete  is  then  finished  and  is  so  applied  as  to  adhere 
perfectly  to  the  sleeper.  At  the  joints  both  the  sleepers  and 
the  rail  base  are  anchored  to  the  concrete.  In  roads  where 
it  is  necessary  to  fix  the  rails  which  become  loose,  and  when 
the  method  just  described  can  not  be  adopted,  a  poured 
bed  of  asphalt  is  provided  under  the  rails  and  the  wedges  on 
which  the  track  rests  are  placed  at  intervals  of  20  inches 
instead  of  about  6  feet. 

Spain.  JOSE  RODRIGUEZ  SPITERI.  The  construction 
of  the  tramway  along  the  road  or  public  highway  brings 
with  it  difficulties,  nuisances  and  even  danger  to  pedestrians 
and  vehicles.  If  the  tramway  must  be  placed  on  the  public 
highway,  it  should  be  placed  on  that  side  which  causes  the 
least  possible  interference  to  the  road  in  the  case  of  a  single 
track  line.  If  it  is  a  double  track,  as  there  is  usually  not 
sufficient  width  to  allow  a  double  track  to  be  constructed 
in  the  center  of  the  roadway,  the  tracks  should  be  placed 
one  on  either  side,  care  being  taken  to  leave  in  the  center 


208  HIGHWAY   ENGINEERING 

a  width  of  about  15  feet  for  the  ordinary  traffic  and  two 
side  clearways  to  the  outside  of  the  rails  which  should  have 
at  least  a  width  of  about  20  inches  beyond  the  profile  of 
the  rolling  stock.  If  the  tracks  are  accessible  to  the  horse 
drawn  traffic,  they  should  be  built  flush  with  the  road 
surface.  In  order  to  fulfill  this  condition  grooved  rails 
must  be  used,  such  as  the  Phoenix  type,  or  they  may  be 
also  of  the  twin  or  double  type.  They  should  be  laid  in 
concrete  beddings  or  on  longitudinal  sleepers.  Wooden 
sleepers  should  be  given  up  because  they  allow  too  great  a 
flexibility  in  the  track.  Metal  sleepers  considerably  in- 
crease the  cost  of  construction  since  they  have  a  short  life. 

The  tramways  of  Spain  are  for  the  most  part  construct- 
ed on  longitudinal  concrete  sleepers,  and  up  to  the  present 
nothing  has  occurred  to  convince  us  that  this  is  not  good 
construction.  Some  people  say  that  the  undulatory  wear 
of  the  rails  is  liable  to  occur  or  is  brought  about  by  a  too 
rigid  foundation.  We  have,  however,  not  been  able  to 
confirm  such  an  opinion  on  the  various  lines  in  Spain. 

Thus  it  appears  to  us  that  the  best  system  of  laying 
a  tramway  track  is  to  place  the  rails  on  a  system  of  con- 
tinuous concrete  blocks,  the  cross-section  of  which  is  pro- 
portionate to  the  resistance  and  the  ground  conditions,  a 
section  measuring  never  less  than  6  inches  in  height,  and 
always  extending  more  than  2  inches  beyond  each  side  of 
the  rail  base. 

Due  to  the  fact  that  the  rail  joint  is  the  weak  spot  in  a 
flush  track,  recourse  should  be  made  to  the  continuous 
track  or  to  some  method  of  directly  welding  the  rail. 

The  ordinary  regulation,  which  allows  railway  com- 
panies to  construct  the  area  between  the  rails  and  the  areas 
in  direct  contact  with  the  adjoining  roadway  with  the 


TRAMWAYS   ON   ROADS   AND   STREETS  209 

same  material  as  is  used  in  the  roadway,  does  not  always 
produce  good  results  even  if  one  row  of  stone  blocks  is  laid 
next  to  the  rail  with  their  greatest  dimension  parallel  to  the 
track.  The  space  between  the  rails  and  the  areas  outside 
of  each  rail  of  about  19}^  inches  in  width  should  be  paved 
with  a  well  selected  material,-  very  hard  and  resistant,  bedded 
on  a  solid  foundation.  Where  reasons  of  an  economic 
character  would  not  permit  of  this  construction,  the  breadth 
of  the  surface  paved  between  the  track  may  be  reduced  to  a 
single  course  of  paving  each  side  of  the  rail,  the  remainder 
of  the  area  to  be  made  up  of  the  same  material  with  which 
the  roadway  is  constructed.  The  rail  track  of  the  tramway 
should  conform  as  much  as  possible  to  the  cross-section  of 
the  road  and  particular  care  should  be  taken  that  the  joints 
of  the  surfaces  should  be  made  in  such  a  manner  as  to  pre- 
vent the  accumulation  of  water. 


CHAPTER   XXI 
PUBLIC  SERVICE  CONVEYANCES 

ALBERTINI,  ANTOINE,  Director  of  Engineering  Depart- 
ment, Province  of  Modena,  Italy. 

DE  HEVESY,   GUILLAUME,   Civil  Engineer,   Budapest, 
Hungary. 

DE  FUISSEAUX,  H.  L.,  Chief  Engineer,  Director  of  the 
Autobus  Company,  Brussels,  Belgium. 

HANSEZ,  JULES,  President,   Touring  Committee,  Royal 
Automobile  Club,  Brussels,  Belgium. 

MARIAGE,  A.,  Chief  Engineer,  Omnibus  Company,  Paris, 
France. 

PERISSE,  LUCIEN,  Engineer  of  Arts  and  Manufactures^ 
Paris,  France. 

SMITH,   EDWARD   SHRAPNELL,    Member   of  Committee^ 
Royal  Automobile  Club,  London,  England,  Great  Britain. 

WILLIAMS,  BENJAMIN  W.,  Councilor  of  the  Borough  of 
Southwark,  Walworth,  London,  England,  Great  Britain. 

Belgium.    H.  L.  DE  FUISSEAUX.    Among  the  advan- 
tages of  the  modern  motorbus  the  following  may  be  cited : 

1.  No  disturbance  to  the  ordinary  traffic. 

2.  The    first    cost    of    establishment    neither    causes 
deterioration  of  the  road  surface  nor  does  it  require  the  devi- 
ation of  public  services  such  as  water,  gas  and  electricity. 

3.  The  maintenance  and  cleansing  of  the  public  high- 

210 


PUBLIC    SERVICE    CONVEYANCES  211 

way  is  easier  than  is  the  case  where  the  rails  of  a  tramway 
occupy  a  portion  of  the  road. 

4.  The  possibility  of  diverting  a  service  readily  at  short 
notice  as  in  the  case  of  processions  or  public  festivals  on 
one  of  the  streets  travelled  over  in  the  regular  route,  the  bus 
passing  through  neighboring  side  streets,  thereby  permit- 
ting the  maintenance  of  traffic  and  the  rapid  handling  of  the 
same. 

5.  No  hindrance  to  the  drawing  up  of  ordinary  vehicles 
at  the  sides  of  the  highways. 

6.  No  danger  from  the  electrolysis  of  gas  and  water 
mains. 

7.  No  danger  of  electrocution. 

8.  Less  danger  of  accidents  by  running  over  people. 

9.  Smaller  cost  of  transportation. 

10.  The  greater  safety  for  people  in  getting  on  and  off, 
as  the  motorbus  can  approach  the  sidewalk  to  take  on  and 
let  off  passengers. 

11.  Fewer  disagreeable  shocks  at   the   curves   or  on 
braking. 

12.  The  greater  regularity  of  running  and  the  assured 
running  while  snow  or  ice  covers  the  streets. 

13.  Less  capital  required  for  the  establishment  of  the 
service. 

14.  Better  revenue  for  the  capital  invested. 

15.  The  possibility  of  creating  provisional  services. 

16.  The  great  facility  in  exploitation. 

The  disadvantages  arising  from  the  use  of  motorbuses 
are  noise,  splashing  of  mud,  dust,  odor  and  vibration. 
Such  objections  as  noise  and  odor  can  be  eliminated  provided 
the  car  is  in  a  proper  state  of  repair  and  the  operator  is 
familiar  with  his  work.  The  vibration  caused  by  the  car 


212  HIGHWAY   ENGINEERING 

is  largely  due  to  the  condition  of  the  road  surface  over 
which  it  passes  and  also  depends  upon  the  type  of  tire  used 
on  the  wheels  and  the  kind  of  springs  with  which  the  car 
is  equipped.  The  dust  nuisance  can  be  avoided  by  properly 
cleaning  the  roads  or  by  treating  them  with  some  suitable 
palliative.  Mud  splashing  will  not  be  a  serious  objection 
if  the  road  surfaces  are  in  good  shape. 

The  following  cost  table  is  based  on  the  assumption 
that  a  vehicle  works  eighteen  hours  every  day  and  runs 
74.5  miles: 

Cost  per  car  mile 

Petrol,  oil,  maintenance $    .  0414 

Maintenance  on  5  year  guarantee 0186 

Chauffeur 0311 

Garage  and  insurance 0186 

Tires..  .0342 


Total $  .1439 

Belgium.  JULES  HANSEZ.  Wherever  the  roadway 
has  a  perfect  surface,  motorbuses  may  render  very  con- 
siderable service.  Where  no  tramways  exist  and  where 
traffic  is  light  the  advantages  of  motorbuses  should  be 
seriously  considered. 

France.  A.  MARIAGE.  In  France  and  her  possessions 
there  are  fifty  lines  on  which  are  operated  some  form  of 
motor  power  bus,  the  lines  varying  from  about  3  miles  to 
317  miles  in  length.  A  majority  of  the  lines  pass  over 
roads  having  maximum  grades  of  6  per  cent  to  9  per  cent 
and  in  one  case  the  maximum  grade  is  12  per  cent. 

With  few  exceptions  the  capacity  of  the  body  of  the 
car  is  between  ten  and  twenty  seats.  The  total  weight  of 
the  loaded  car  is  usually  between  6,614  and  13,228  pounds, 
with  an  almost  constant  axle  load  distribution  of  one-third 
on  the  front  axle  and  two-thirds  on  the  back  axle.  The 


PUBLIC    SERVICE    CONVEYANCES  213 

power  for  these  vehicles  is  supplied  in  the  large  majority  of 
cases  by  gas  engines  but  there  are  a  few  instances  where 
steam  is  used,  generated  either  by  a  liquid  or  a  solid  fuel. 
The  power  of  the  motors  varies  from  12  to  40  horse-power, 
capable  of  attaining  speeds  from  8  to  25  miles  an  hour. 
The  cars  never  have  more  than  two  axles  except  in  the  case 
of  the  Renard  system,  where  three  axles  are  used  on  the 
trailers.  The  steering  wheels  are  the  two  front  wheels,  the 
two  back  wheels  being  the  driving  wheels.  The  tires  used 
may  be  either  pneumatic,  solid  rubber,  rubber  blocks  in- 
serted in  the  rim,  iron  or  steel.  Although  the  pneumatic 
tire  affords  the  easier  riding,  it  cannot  be  used  with  economy 
except  on  light  cars  and  the  solid  rubber  tire  is  therefore 
the  most  common  form  of  elastic  tire.  In  order  to  prevent 
skidding  the  rims  of  the  back  wheels  are  divided  into  two 
parts.  The  Renard  system,  which  is  mentioned  above,  is 
used  on  two  lines  and  is  practically  the  only  system  employ- 
ing trailers.  The  principle  of  the  Renard  system  is  to  have 
one  motor  car  capable  of  developing  and  transmitting 
power  to  each  trailer  forming  the  train  so  that  each  trailer 
is  operated  independently. 

At  the  15th  International  Tramway  and  Light  Railway 
Congress  held  at  Munich  in  September,  1908,  the  general 
reply  to  a  question  concerning  the  additional  expenses  for 
maintaining  a  road  under  a  motorbus  service  was  that  an 
increase  of  expenses  was  necessary.  In  Corsica,  the  supple- 
mentary expenditure  is  estimated  at  $15.50  per  mile  per 
annum  and  in  C6tes-du-Nord  at  3.1  cents  per  mile  run. 
In  the  Vendee  the  rural  roads  have  been  completely  cut  up 
and  the  administrative  bodies  estimate  about  $1,930  for  each 
20  miles  as  the  supplementary  expense  of  maintenance.  In 
this  last  case,  however,  the  vehicles  were  fitted  with  iron  tires. 


214  HIGHWAY   ENGINEERING 

The  writer  collected  information  relative  to  public 
motor  conveyances  in  several  districts  in  France  where 
such  vehicles  were  used.  As  a  result  it  was  found  that  they 
had  only  recently  attained  a  certain  success.  In  general 
the  results  of  exploitation  were  not  very  encouraging,  due 
to  the  very  high  costs  of  operation.  Since  the  costs  are 
high,  the  traffic  is  restricted  and  the  returns  small,  resulting 
sometimes  in  a  loss. 

The  writer  does  not  think  that  motorbuses  and  railways 
can  be  compared  as  neither  one  can  be  substituted  for  the 
other.  The  motorbus  is  desirable  when  the  running  ex- 
penses are  immaterial  such  as  for  pleasure  trips  and  when 
creating  a  traffic  prior  to  building  a  railway.  The  only 
advantage  the  motorbus  has  over  tramways  at  present  is 
the  lower  initial  cost. 

France.  LUCIEN  PERISSE.  The  writer  believes  that 
two  distinct  classes  of  public  motor  conveyances  should  be 
recognized,  the  first  class  to  include  those  used  in  large 
cities  or  towns  and  the  second  class  those  applicable  to 
interurban  use.  The  second  class  may  be  considered  to 
include  the  motor  omnibus  which  can  render  great  service 
outside  of  towns,  principally  in  making  connections  or 
acting  as  feeders  between  the  stations  of  the  main  lines  of 
the  great  railway  companies  for  the  transport  of  passengers 
and  light  weight  goods.  Further,  in  certain  cases  and 
at  favorable  seasons,  such  means  of  conveyance  should 
serve  to  bring  a  stream  of  tourists  to  new  centers  and  to 
the  picturesque  watering  places.  Lines  of  omnibuses  can 
also  serve  as  direct  connecting  links  between  two  important 
centers  which  have  only  an  indirect  intercommunication 
by  rail. 

In  the  country  where  it  is  not  possible  to  think  of  paving 


PUBLIC    SERVICE    CONVEYANCES  215 

many  miles  of  roads,  it  is  necessary  to  increase  the  resistance 
of  the  roadway  used  by  motor  conveyances  by  judicious 
choice  of  materials  in  its  construction. 

Great  Britain.  EDWARD  SHRAPNELL  SMITH.  The  out- 
standing advantages  of  the  motorbus,  which  are  peculiar 
to  it  in  comparison  with  the  electric  tramcar,  include: 

1.  Low  capital  outlay  involved. 

2.  Absence  of  the  necessity  of  obtaining  special  powers 
from  the  legislature. 

3.  Mobility  of  rolling  stock. 

4.  Independence  of  a  central  power  plant. 

5.  Non-interference  with  other  traffic. 

6.  No  rails  and  no  overhead  equipment. 

7.  Low  working  costs  now  achieved. 

Advocates  of  electric  traction  four  and  more  years  ago, 
at  the  time  when  motorbus  operation  was  still  in  its  infancy, 
had  seven  chief  points  of  attack,  as  follows: 

1.  Great  noise  and  consequent  inconvenience  to  other 
users  of  the  road  and  to  those  residing  along  the  streets 
where  they  are  operated. 

2.  Odor. 

3.  The  ever  present  danger  of  side-slip. 

4.  The  danger  of  fire. 

5.  Vibration. 

6.  Danger  to  other  vehicles  on  the  highway. 

7.  Unreliability. 

To-day  there  is  no  justification  for  these  objections. 

Sir  Herbert  Jekyll,  K.  C.  M.  G.,  the  Head  of  the  Lon- 
don Traffic  Branch  of  the  Board  of  Trade,  in  a  report  is- 
sued in  January,  1910,  said:  "As  rivals  to  tramways,  motor 
omnibuses  are  likely  to  become  more  formidable  than  they 
have  been  hitherto,  since  they  will  be  cheaper  to  work,  and 


216  HIGHWAY  ENGINEERING 

will  travel  longer  distances  than  heretofore.  Tramways 
have  long  since  reached  a  stage  at  which  there  would  appear 
to  be  little  room  for  further  improvement  either  in  efficiency 
or  cheapness.  Motor  omnibuses,  on  the  other  hand,  are 
only  beginning  to  show  their  capacity  for  dealing  with 
traffic  in  large  volume,  and  there  is  still  an  ample  margin 
for  improvement.  As  a  means  of  transportation,  the 
omnibus  is  in  its  infancy,  whereas  the  tramway  has  come 
to  maturity." 

The  London  General  Omnibus  Co.,  Ltd.,  has  not  failed 
to  pay  dividends  in  the  past  three  years.  This  company 
owns  fully  1,000  motorbuses  which  will  all  be  put  into  ser- 
vice during  the  summer  of  1910. 

In  London  not  infrequently  at  the  busiest  hour  of  the 
day  as  many  as  9,000  passengers  per  hour  are  conveyed 
along  certain  thoroughfares  by  motorbuses,  having  thirty- 
four  seats.  A  bus  can  not  carry  standing  passengers  either 
inside  or  elsewhere.  With  larger  bodies  the  writer  sees  no 
reason  why  the  capacity  for  passenger  traffic  by  means  of 
jnotorbus  cannot  be  safely  put  as  high  as  20,000  passengers 
per  hour  in  each  direction  where  there  is  a  call  for  such  con- 
centration. 

Great  Britain.  BENJAMIN  W.  WILLIAMS.  The  number 
of  passengers  carried  in  London  last  year  varied  from  700 
to  800  millions  of  which  300  millions  were  carried  by  motor- 
buses.  Tramways  and  motorbuses  must  be  considered  as 
modes  of  transport  which  have  advantages  over  one  another 
according  to  the  districts  which  they  serve.  The  traffic  of 
these  motorbuses  has  no  special  effect  upon  the  road  owing 
to  the  existence  of  ordinary  automobile  traffic.  The  roads 
must  be  constructed  in  accordance  with  the  requirements 
of  this  class  of  traffic. 


PUBLIC    SERVICE    CONVEYANCES  217 

Hungary.  GUILLAUME  DE  HEVESY.  The  Hungarian 
government  is  experimenting  with  a  motorbus  train  after 
the  Renard  type,  consisting  of  two  driving  cars  of  70  horse- 
power each,  four  trailers  each  carrying  a -load  of  3.5  tons 
and  a  residence  car.  It  is  intended  to  use  this  train  in 
maintaining  a  stretch  of  government  road  about  155  miles 
in  length  in  the  County  of  Pest  and  this  system  is  expected 
to  show  a  large  saving  in  the  cost  of  transportation  of  road 
material. 

The  writer  thinks  that  the  special  field  for  the  utiliza- 
tion of  the  motorbus  is  in  those  branches  of  activity  where 
the  introduction  of  cheap  transport  by  road  would  be  of 
great  advantage,  as  for  example  in: 

1.  The    building    industry    including    brick    factories, 
motor  and  cement  works,  stone  and  asphalt  industries,  etc. 

2.  The  exploitation  of  mines,  including  quarries. 

3.  The  transportation  of  raw  materials  for  factories. 

4.  The  delivery  of  wood,  coal,  etc. 

5.  The  transportation  of  food  stuffs  for  the  towns. 

6.  The  transportation  of  agricultural  raw  materials. 

7.  The  lumber  industries. 

Italy.  ANTOINE  ALBERTINI.  The  Maranello-Pavullo 
line  has  been  successfully  operated  in  the  Province  of 
Modena,  Italy,  since  1906,  and  furnishes  a  motorbus  service 
using  cars  with  a  capacity  of  twelve  to  twenty-four  pas- 
sengers. 

If  by  means  of  a  motor  service  for  passengers  only,  like 
those  in  Italy,  a  sensible  increase,  constant  and  regular, 
occurs  in  the  ordinary  number  of  travellers  over  a  certain 
route,  the  laying  down  of  a  tramway  or  railway  might  be 
justified.  For  the  success  of  such  a  service  gives  proof  of 
the  existence  of  a  latent,  economic  potentiality,  which  only 


218  HIGHWAY   ENGINEERING 

awaits  the  means  to  enable  it  to  be  revealed  for  the  good  of 
the  inhabitants.  This  is  the  principal  advantage  that  will 
be  derived  from  a  motorbus  service.  A  public  automobile 
service  cannot  therefore  be  considered  a  permanent  one 
either  in  populous  districts  or  in  those  mainly  devoted  to 
agriculture;  it  is  only  a  temporary  arrangement. 

Before  the  installation  of  public  motorbus  services,  the 
road  to  be  used  should  be  prepared  and  adapted  to  such 
service.  Provisions  should  be  made  for  the  maintenance 
of  the  road  by  spreading  fresh  layers  of  stone  over  the 
whole  surface  and  rolling  it. 


CHAPTER  XXII 

~— ^ — 

HIGHWAY  BRIDGES 

BEAUMONT,  W.  WORBY,  M.  Inst.  C.  E.,   Consulting 
Engineer,  London,  England,  Great  Britain. 

CHRISTOPHE,  PAUL,  Principal  Engineer  of  Bridges  and 
Roads,  Brussels,  Belgium. 

DE  NOVAK,  FRANCOIS,  Technical  Councilor  to  the  Royal 
Ministry,  Budapest,  Hungary. 

DESCANS,  LEON,  Engineer  of  Bridges  and  Roads,  Ghent, 
Belgium. 

RESAL,  JEAN,  Inspector-General  of  Bridges  and  Roads, 
Paris,  France. 

Belgium.  PAUL  CHRISTOPHE.  On  the  Government 
roads  in  Belgium,  bridges  must  be  calculated  first  for  a 
uniformly  distributed  load  of  82  pounds  per  square  foot  and, 
next,  for  a  load  of  18  tons  on  two  axles.  If  the  travelled 
way  is  wide  enough  to  accommodate  them,  the  bridge  shall 
be  calculated  for  two  such  axle  loadings  side  by  side.  The 
axles  are  about  10  feet  center  to  center  and  the  rear  axle 
is  assumed  to  carry  10  tons.  The  gauge  of  the  wheels  of 
both  axles  is  to  be  taken  as  5.6  feet  and  the  distance  between 
two  trucks  side  by  side  5.2  feet.  Each  truck  is  supposed 
to  be  drawn  by  ten  horses,  each  animal  weighing  1,543 
pounds.  The  total  weight  of  the  truck  and  team  is,  there- 
fore, 25  tons.  This  load  is  distributed  over  an  area  of  60.7 
feet  by  10.8  feet.  If  trucks  with  their  teams  are  replaced 

219 


220  HIGHWAY   ENGINEERING 

by  auto  trucks  of  the  same  weight  and  the  same  conditions 
of  crowding  are  allowed  on  the  bridge  as  under  the  present 
regulations,  the  auto  trucks  will  strain  the  bridge  more 
due  to  the  closer  spacing  of  the  loads. 

Motor  cars  of  the  lighter  type  have  no  influence  on  the 
elasticity  of  bridges  since  the  vibrations  they  produce  are 
absolutely  imperceptible.  With  regard  to  heavy  motor 
vehicles  no  conclusions  can  be  drawn  because  the  experi- 
ments carried  out  with  them  are  not  very  numerous.  Al- 
though speed  is  able  to  accentuate  to  a  sufficiently  noticeable 
extent  the  effect  of  rolling  loads  on  bridges,  there  is  nothing 
that  would  lead  the  writer  to  suppose  that  the  progress  of 
automobilism  would  aggravate  the  situation,  unless  very 
heavy  engines  come  into  a  more  general  use  as  a  means  of 
conveyance. 

The  writer  has  concluded  from  tests  made  under  his 
direction  that  if  the  various  members  of  a  metallic  bridge  are 
firmly  held  together  to  form  a  perfectly  united  whole,  they 
can  be  made  just  as  rigid,  and  are  consequently  able  to  resist 
the  dynamic  effects  of  rolling  loads  just  as  effectually  as 
bridges  of  reinforced  concrete,  for  which  a  superiority  in 
this  respect  is  sometimes  claimed. 

Belgium.  LEON  DESCANS.  The  stringers  of  bridges 
will  act  in  one  of  the  three  following  ways  dependent  upon 
the  end  connections: 

1.  As  a  beam  simply  supported  at  the  ends. 

2.  As  a  continuous  beam  with  the  ends  free  to  rotate. 

3.  As  a  continuous  beam  with  the  ends  fixed. 

From  calculations  it  may  be  proved  that  under  certain 
assumptions  the  continuity  of  the  stringers  will  reduce  the 
deflections  of  the  floor  by  about  one-half  under  the  passage 
of  rolling  loads.  The  continuity  of  the  stringers  combined 


HIGHWAY  BRIDGES  221 

with  a  system  of  connections  with  the  cross  girders,  which 
will  prevent  the  rotation  of  the  stringers  over  the  points  of 
support,  will  reduce  the  deflections  to  about  one-quarter  of 
their  original  values.  It  is,  therefore,  desirable  that  the 
connections  between  stringers  and  cross  girders  should  be  as 
rigid  as  possible.  The  connections  between  the  stringers 
and  cross  girders  must  be  calculated  with  a  view  to  make 
them  strong  enough  to  resist  the  bending  moments  in  the 
stringers  as  continuous  girders.  Although  the  continuity 
of  the  stringers  necessitates  the  strengthening  of  the  connec- 
tions, it  reduces,  on  the  other  hand,  the  maximum  bending 
moments  in  these  members.  Nevertheless,  it  will  be  advis- 
able to  design  the  stringers  on  the  assumption  that  each 
span  is  an  independent  beam,  merely  .supported  at  the  ends, 
due  to  the  fact  that  the  stiffness  really  due  to  the  supports 
and  the  strains  produced  thereby  are  only  imperfectly 
known. 

France.  JEAN  RESAL.  On  special  structures  of  ma- 
sonry, where  the  dead  load  is  very  considerable  in  comparison 
with  the  weight  of  the  heaviest  vehicles  which  may  circulate 
on  the  roads,  the  influence  of  weight  should  be  considered  as 
negligible. 

On  special  structures  of  reinforced  concrete  it  does  not 
seem  that  an  opinion  deserving  full  confidence  can  be 
expressed  at  the  present  moment,  since  this  method  of 
construction  has  been  practiced  for  too  short  a  period  to 
allow  a  formal  conclusion  to  be  deduced. 

There  remain  bridges  constructed  of  metal  or  wood,  on 
which  subject  theory  and  practice  furnish  data  sufficiently 
complete  and  precise  to  permit  an  answer  to  be  given  to  the 
question  raised.  The  conclusions,  which  we  shall  be  led 
to  draw  from  a  study  of  this  subject,  can  be  extended,  at 


222  HIGHWAY   ENGINEERING 

least  provisionally,  to  reinforced  concrete  structures,  under 
reservation  of  new  facts,  which  in  the  future  will  either 
complete  or  modify  the  still  very  imperfect  knowledge  which 
we  have  of  the  elastic  properties  of  the  hybrid  material. 

In  the  case  of  steel  bridges  the  theory  of  the  effect  of  a 
moving  load  on  the  bridge  is  that  the  vibrations  caused  by 
such  a  load  in  the  course  of  time  weaken  the  metal  by  a 
molecular  transformation  which  makes  the  metal  brittle. 
The  writer  believes  that  this  would  only  occur  if  the  vibra- 
tions have  the  effect  of  increasing  the  elastic  work  up  to  the 
elastic  limit,  or  in  the  case  of  metal  that  is  not  properly 
manufactured. 

There  are  in  existence  many  large  steel  bridges  which 
apparently  show  no  signs  of  crystallization  of  the  metal 
even  though  they  have  been  subjected  to  moving  loads 
whose  weights  and  velocities  have  been  increased  in  a 
marked  degree  since  the  construction  of  the  bridges.  This 
fact  may  be  due  to  the  margin  of  safety,  or  factor  of  safety, 
as  it  is  commonly  called.  Provided  that  the  metal  in  the 
bridge  is  of  the  proper  kind  and  the  workmanship,  par- 
ticularly the  riveting,  is  properly  done,  the  writer  believes 
that  experience  shows  the  practice  followed  by  designers 
insures  proper  stability.  Since  high  speeds  will  only  be 
attainable  by  automobiles  equipped  with  elastic  tires,  it 
seems  inadmissible  that  the  fastest  cars,  whatever  their 
weight,  limited  moreover  by  the  necessity  of  having  an 
expensive  tire,  should  be  capable  of  subjecting  a  bridge  to 
shocks  comparable  with  those  which  it  actually  sustains 
from  the  passage  of  ordinary  wheel  traffic. 

Great  Britain.  W.  WORBY  BEAUMONT.  Upon  a  per- 
fectly smooth  road  surface  vehicles  with  smooth  metal  tires 
or  rubber  tires  would  not  give  rise  to  impact  forces.  Im- 


HIGHWAY   BRIDGES  223 

perfection  of  balance  of  the  motor  machinery  may  be 
omitted  from  consideration  in  this  question  with  regard  to 
a  perfect  road  surface  or  an  ordinary  road  surface.  Im- 
perfections of  road  surface  must,  therefore,  be  looked  upon 
as  the  primary  cause  of  the  interacting  disturbances  set  up 
by  the  passage  of  motor  vehicles.  These  disturbances 
increase  as  the  weight  of  the  vehicle,  as  the  square  of  its 
velocity,  and  in  various  ratios  greater  than  arithmetical 
proportion  with  the  increase  in  roughness  and  irregularity 
of  the  road  surface. 

In  general  it  may  be  said  that  in  questions  involving 
consideration  of  harmful  vibrations  created  by  the  passage 
of  heavy  vehicles  over  common  roads,  greater  attention 
should  be  directed  to  the  limitation  of  speed  than  to  the 
limitation  of  weight,  provided  that  the  latter  is  within  the 
limits  now  laid  down  by  the  authorities  in  the  United 
Kingdom.  That  attention  has  been  properly  directed  to 
these  limits  is  sufficiently  shown  by  the  following  figures  of 
maximum  speed  and  weight  as  now  authorized: 

Total  Weight       Maximum 
of  Vehicle         Speed  Per- 
and  Loads  in          mitted. 

Tons  Miles  per  Hour    Material  of  Comparison  of 

Nos.  (W)  (V) 

1           12  5 

29  8 

3          12  8 

49  12 

5            3.5  20 

These  figures  suffice  to  show  that  the  product  of  W 
and  V2,  which  is  an  index  of  the  violence  of  impact,  is  greater 
with  the  lighter  vehicles  at  their  higher  permitted  speeds 
than  with  the  heavier  at  their  lower  allowed  speeds,  and  that 
as  the  load  becomes  greater  and  therefore  approaches  more 
closely  the  limit  of  load  which  the  road  will  carry  without 


Tires 

WV2 

Momentum 

Weight 

Iron 

300 

1.00 

3.43 

14 

576 

1.92 

2.57 

Rubber 

768 

2.56 

3.43 

tt 

1296 

4.33 

2.57 

(f 

1400 

4.67 

1.00 

224  HIGHWAY   ENGINEERING 

injury  to  foundation  or  displacement  of  subsoil,  so  the  dis- 
turbance due  to  impact  is  lessened  by  reduction  of  speed  in 
a  greater  inverse  ratio  than  that  due  to  the  ratio  of  increase 
of  weight. 

Hungary.  FRANgois  DE  NOVAK.  Regulations  are  in 
force  in  Hungary  which  govern  the  design  and  the  use  of 
the  highway  bridges.  Bridges  of  the  lowest  class  are  de- 
signed for  vehicles  weighing  from  3  to  6  tons,  while  bridges 
of  the  first  class  are  designed  for  loads  of  12  to  24  tons. 
It  has  been  observed  on  one  bridge  that  a  steam-roller 
weighing  13.5  tons  did  not  produce  as  much  oscillation  as  a 
horse  drawn  vehicle  weighing  1.5  tons,  due  to  the  rhythmic 
motion  of  the  animals.  The  dynamic  effect  of  an  auto- 
mobile differs  from  that  of  a  horse  drawn  vehicle  and 
although  the  motor  cars  travel  at  greater  speeds,  the  fact 
that  they  are  provided  with  pneumatic  tires  prevents  as 
great  a  dynamic  effect  being  produced.  A  sudden  applica- 
tion of  the  brakes  of  a  motor  car  while  on  the  bridge  may 
cause  a  considerable  shock  to  a  small  structure,  but  the 
road  bridge  covering  can  generally  resist  these  forces. 


CHAPTER  XXIII 

TIRES 

ARISI,  T.,  Engineer;  Member,  Automobile  Club  of  Italy, 
Italy. 

BAUDRY  DE  SAUNIER,  L.,  Member,  Automobile  Club  of 
France,  France. 

FERRUS,  COMMANDANT  L.,  Member,  Automobile  Club  of 
France,  France. 

HANSEZ,  JULES,  President,  Touring  Committee,  Royal 
Automobile  Club,  Brussels,  Belgium. 

JANSON,  J.  H.,  Secretary  of  the  Touring  Club  of  Nether- 
lands, Netherlands. 

LUMET,  GEORGES,  Engineer  of  Arts  and  Manufactures, 
Paris,  France. 

MALLOCK,  A.,  E.  R.  S.,  Royal  Automobile  Club,  London, 
England,  Great  Britain. 

STEFFELAAR,  L.  C.,  President  of  the  Touring  Club  of 
Netherlands,  Netherlands. 

Belgium.  JULES  HANSEZ.  The  action  of  a  pneumatic 
tire  on  the  road  surface  is  mainly  frictional,  due  to  the  fact 
that  at  certain  speeds  the  wheels  jump,  owing  to  the  in- 
equality of  the  road  surface  and  the  elastic  deformation  of 
the  tire.  Trials  have  been  made  with  distance  recorders 
and  it  was  found  that  the  distance  indicated  between  two 
towns  was  greater  with  the  smooth  than  with  the  non- 
skidding  tires.  In  skidding  the  wheels  do  much  more  dam- 

225 


226  HIGHWAY  ENGINEERING 

age  to  the  road  surface  than  in  rolling.  In  wet  weather  a 
non-skidding  tread  is  indispensable  to  the  safety  of  the  pas- 
sengers. Chains,  steel  rivets  and  rubber  studs  are  some  of 
the  devices  used  to  prevent  skidding.  The  leather  cover 
studded  with  steel  rivets  is  the  most  popular  form  for  use 
on  the  pneumatic  tire.  For  large  and  powerful  vehicles  the 
writer  recommends  twin  pneumatic  tires  on  each  rear  wheel. 
The  advantages  in  favor  of  twin  tires  are  many,  both  from 
the  standpoint  of  the  automobile  and  the  road.  ^ 

France.  COMMANDANT  L.  FERRUS.  Pneumatic  tires 
furnish  comfortable  riding,  preserve  the  machinery,  per- 
mit the  use  of  much  higher  speeds,  and  produce  a  saving 
in  tractive  force.  As  a  result  of  experiments  made  with 
different  makes  of  tires  for  different  speeds  and  for  air 
pressures  in  the  tubes  of  about  13  pounds  and  5  pounds,  it 
has  been  found  that  the  best  solid  tire  required  practically 
the  same  tractive  force  as  the  best  pneumatic  tire  and  that 
the  tractive  force  increases  when  the  air  pressure  in  the 
tube  drops  from  13  to  5  pounds. 

Since  pneumatic  tires  cannot,  as  a  rule,  be  subjected  to 
pressures  of  more  than  1,300  pounds,  their  use  will  be 
limited  to  light  vehicles.  Experiments  have  been  made  in 
France  by  the  Compagnie  Generale  des  Omnibus  in  fitting 
their  5  ton  omnibuses  with  twin  pneumatic  tires.  Excellent 
results  have  been  obtained  with  respect  to  comfortable 
riding,  but  the  cost  of  the  tires  in  this  particular  experiment 
has  proved  to  be  absolutely  prohibitive. 

Solid  tires  in  actual  use  may  be  divided  into  three  main 
classes: 

1.  Continuous  hoops  of  a  half  round  or  nearly  half 
round  section  vulcanized  on  the  rim.  These  may  be  used 
either  as  single  or  twin  tires. 


TIRES  227 

2.  Continuous  hoops,  generally  of  trapezoidal  section 
and  fixed  to  the  rim  by  steel  rods.     These  tires  may  also 
be  of  the  single  or  twin  type. 

3.  Sectional  tires  or  blocks. 

Continuous  tires  have  a  very  serious  fault  when  used 
on  heavy  motor  omnibuses,  such  as  those  commonly  running 
in  cities  like  Paris,  as  they  are  too  liable  to  skid  when  the 
pavement  is  at  all  greasy.  Skidding  is  very  much  less 
pronounced  when  the  wheels  are  fitted  with  twin  tires. 
On  the  other  hand  blocks  have  given  every  satisfaction 
with  respect  to  non-skidding,  but  they  are  not  as  satisfactory 
as  continuous  hoops  with  respect  to  the  absence  of  vibration. 
The  tires  with  rod  fastenings  have  the  same  advantages 
and  disadvantages  as  the  hoops  vulcanized  on  the  rim. 

A  spring  wheel  is  a  wheel  that  is  deformed  elastically 
in  such  a  manner  as  to  take  up  all  the  jolts  of  the  road  with- 
out ceasing  to  fulfil  its  ordinary  duty.  There  are  many 
different  types  of  these  wheels,  some  have  rigid  outer  rims 
and  develop  the  elastic  feature  from  the  center  of  the  wheel 
by  means  of  air,  others  use  an  elastic  material  on  the  rim, 
which  would  include  wheels  equipped  with  any  form  of 
rubber  tire.  Still  another  type  is  the  elastic  wheel  with 
the  non-continuous  flexible  outer  rim  such  as  the  Brillie 
wheel  with  radial  pistons  supported  on  round  india  rubber 
pads.  There  are  only  two  types  of  these  wheels  that  show 
signs  of  satisfying  the  requirements  for  motor  cars.  They 
are  the  Lipkouske  and  the  Partington  wheel. 

France.  GEORGES  LUMET.  The  weight,  width  of 
tires,  diameter  of  wheels  and  the  speed  of  a  vehicle  are  all 
factors  which  affect  the  life  of  a  road.  The  consideration 
of  speed  is  not  of  as  much  importance  in  the  case  of  horse 
drawn  vehicles  as  it  is  in  the  case  of  those  mechanically 


228  HIGHWAY   ENGINEERING 

driven.  If  the  relation  between  the  load  carried,  the 
width  of  tires  and  the  diameters  of  the  wheels  is  properly 
fixed  for  horse  drawn  vehicles,  they  should  not  cause  extra- 
ordinary damage  to  the  roads.  The  high  speeds  at  which 
motor  vehicles  travel,  however,  accentuate  the  effect  of  the 
vibrations  of  the  car  which  otherwise  would  not  be  at  all 
deleterious. 

It  is  the  writer's  opinion  that  industrial  transport  by 
means  of  motor  vehicles,  with  engines  working  with  ex- 
plosive mixtures,  cannot  cause  any  damage  to  the  road 
surface  provided  they  are  kept  within  the  following  limits 
as  regards  speed  and  weight: 

Class  1.  Average  speed  10  miles  an  hour;  maximum 
speed  15.5  miles  an  hour. 

Greatest  pressure  on  the  tires  per  inch  of  length  of  the 
circumference  in  contact  with  the  ground,  to  be  equal  to 
840  pounds,  with  wheels  not  exceeding  3.28  feet  in  diame- 
ter. Greatest  width  of  tire,  6  inches. 

Class  2.  Average  speed  6  miles  an  hour;  maximum 
speed  9  miles  an  hour. 

Greatest  pressure  on  the  tires  per  inch  of  length  of  the 
circumference  in  contact  with  the  ground,  to  be  equal  to 
840  pounds,  with  wheels  not  exceeding  3.25  feet  in  diameter. 
Greatest  width  of  tires  specified  is  applicable  to  those  rubber 
tires  in  which  the  rubber  is  in  contact  with  the  ground. 
For  other  tires  it  will  be  necessary  to  ascertain  by  experi- 
ment the  greatest  width  to  be  prescribed  so  that  the  dis- 
tribution of  the  load  on  the  ground  may  be  effected  under 
normal  conditions. 

The  writer  believes  that  some  form  of  armored  tire 
may  prove  to  be  less  destructive  to  a  road  surface  than  the 
smooth  tire,  since  it  prevents  slipping  of  the  wheel.  It 


TIRES  229 

is  known  that  where  a  wheel  revolves  on  the  same  spot, 
through  want  of  adhesion  or  by  reason  of  its  leaving  the 
ground,  it  may  be  made  to  slip  sideways  by  a  slight  lateral 
push  and  may  give  rise,  in  this  way,  to  very  destructive 
transverse  forces. 

The  sudden  starting  or  braking  of  a  car  causes  serious 
wear  to  the  road.  The  application  of  the  brake  should 
produce  a  retarding  force  on  the  drum  in  order  that  work 
may  be  produced,  the  result  of  the  friction  between  the 
strap  of  the  brake  and  the  drum.  It  is  this  work  which 
counterbalances  the  kinetic  energy  of  the  vehicle,  and  it  is 
easily  understood  that  it  is  more  advantageous  to  collect 
this  in  a  part  of  the  machine  specially  provided  for  this 
purpose,  than  to  let  it  expend  itself  as  friction  between  the 
wheel  and  the  road,  to  the  great  detriment  of  both. 

France.  L.  BAUDRY  DE  SAUNTER.  The  principal 
duty  of  the  soft  tire  is  to  absorb  the  lateral  reactions  to  which 
a  vehicle  is  exposed,  and  which  greatly  hinder  its  progress. 
Consequently  the  soft  tire,  although  it  does  increase  the 
coefficient  of  rolling  friction  eliminates  the  numerous  small 
retarding  lateral  forces  to  which  the  vehicle  is  subjected. 

Great  Britain.  A.  MALLOCK.  When  there  is  loose 
material  on  a  road  surface,  any  traffic  will  cause  deteriora- 
tion, but  if  the  surface  is  free  from  loose  pieces  and  is  held 
together  by  some  elastic  or  viscous  binding  material,  wear 
does  not  take  place  unless  the  intensity  of  the  pressure  is 
sufficient : 

1.  To  disintegrate  by  crushing  the  stones  of  which  the 
road  is  formed; 

2.  Or  to  cause  some  permanent  displacement  of  the 
binding  material. 

When  iron  tires  are  used  the  intensity  of  the  pressure 


230  HIGHWAY   ENGINEERING 

at  more  than  very  low  speeds  is  always  greater  than  that 
required  to  satisfy  the  first  condition.  With  soft  tires  the 
case  is  very  different.  The  intensity  of  the  pressure  is  then 
so  light,  not  exceeding  100  or  200  pounds  per  square  inch 
as  against  the  2,000  or  3,000  pounds  per  square  inch  exerted 
even  at  low  speed  by  iron  tires,  that  there  is  no  difficulty 
in  getting  a  surface  which  is  not  affected,  and  for  a  road 
intended  for  soft  tires  only  there  would  be  no  occasion  for 
using  hard  stone.  For  some  time  to  come,  however,  hard 
tires  and  horse  traction  will,  in  the  country  at  any  rate, 
form  a  considerable  part  of  the  traffic,  and  the  roads 
must  be  adapted  to  both  classes. 

Italy.  T.  ARISI.  The  supremacy  of  the  pneumatic 
tire  must  be  considered  not  only  with  regard  to  the  better 
working  of  the  machinery,  but  also  with  regard  to  the 
smaller  fuel  consumption  and  the  road  maintenance.  Sev- 
eral trials  have  clearly  shown  a  saving  in  petrol  of  at  least 
20  per  cent  in  a  vehicle  fitted  with  pneumatic  tires,  probably 
due  to  these  tires  admitting  the  use  of  lighter  wheels  and 
transmission  gear. 

Many  attempts  have  been  made  to  provide  a  substitute 
for  the  pneumatic  tire  by  means  of  spring  wheels  and 
suspensions  but  unfortunately  all  such  devices  have  serious 
defects.  Satisfactory  trials  allow  us  to  hope  that  the 
pneumatic  tire  will  come  into  general  use  for  heavy  loads. 
With  the  use  of  twin  tires  and  by  reducing  the  weight  of 
the  chassis  to  perhaps  2,500  pounds,  a  load  of  4,500  pounds, 
body  included,  could  be  supported. 

Netherlands.  L.  C.  STEFFELAAR  and  J.  H.  JANSON. 
The  Netherlands  is  an  agricultural  country  devoted  ex- 
tensively to  the  cultivation  of  beet  root.  Due  to  the  fact 
that  the  crops  of  this  product  are  all  handled  during  a  very 


TIRES  231 

limited  period,  the  roads  suffer  excessive  damage  and  often- 
times become  impassable  for  every  other  kind  of  traffic. 

To  remedy  conditions  the  Touring  Club  of  Netherlands 
suggested  for  adoption  a  set  of  laws  regulating  the  width  of 
tire,  diameter  of  wheels,  and  weight  of  load.  The  laws, 
however,  were  only  adopted  in  one  province.  With  regard 
to  the  diameter  of  wheels  and  the  widths  of  tires  the  follow- 
ing regulations  were  proposed:  the  maximum  load  including 
the  weight  of  the  vehicle  which  may  travel  on  a  road,  is  to 
be  565  pounds  per  inch  width  of  tire  for  two  wheeled  vehicles, 
the  wheels  of  which  have  a  diameter  of  not  less  than  4  feet, 
3  inches.  The  maximum  load  which  may  travel  on  a  road 
in  the  case  of  vehicles  with  four  or  more  wheels  having  a 
diameter  of  not  less  than  2  feet  8  inches,  shall  be  425  pounds 
per  inch  width  of  tire,  provided  that  the  load  is  divided 
among  the  axles  proportionally  to  their  wheel  diameters. 
In  times  of  thaw  these  loads  are  to  be  reduced  one-half. 


CHAPTER  XXIV 

CONCLUSIONS  ADOPTED  AT  THE  SECOND  CONGRESS 

First  Question 

METALLED  AND  PAVED  ROADS.  USE  OF  BINDING 
MATERIALS  IN  THE  CONSTRUCTION  OF  METALLED  ROADS. 
USE  OF  TRACKWAYS  IN  THE  PAVED  ROADS.  PROGRESS 
MADE  IN  COMBATING  WEAR  AND  TEAR  AND  DUST. 

1.  Use  of  binding  materials  in  the  construction  of 
metalled  roads.  The  Congress  believes  that  it  is  desirable 
to  pursue  and  develop  the  applications  of  the  use  of  binding 
materials  in  the  construction  of  metalled  roadways,  special 
attention  being  given: 

a.  To  determine  the  character  of  the  binder  best  suited 

to  local  conditions  in  each  case; 

b.  To  determine  as  far  as  possible  the  proper  physical 

and  chemical  characteristics  to  be  specified  for 
bituminous  binders; 

c.  To  compare  the  different  results  obtained  by  various 

methods  of  construction; 

d.  To  investigate  the  influence  that  the  storing  of 

tarred  metal  for  a  more  or  less  extended  period  be- 
fore being  used  may  have  upon  the  finished  work; 

e.  To  make  a  study  of  the  deterioration  which  the 

materials  are  subjected  to  during  use; 

f.  To  specify  the  system  to  be  recommended  where 

ordinary  metalling  has  proved  deficient  and  stone 
paving  can  not  for  some  reason  be  adopted; 

232 


CONCLUSIONS   OF  THE    SECOND    CONGRESS  233 

g.  To  determine  for  each  section  of  highway  in  a  given 
district  the  relation  between  cost  and  the  results 
obtained  under  known  local  conditions. 

2.  Use  of  trackways  in  paved  roads.     Except  in  ex- 
ceptional cases  the  construction  of  trackways  hi  paved 
roadways  can  only  be  considered  an  expedient. 

3.  Progress  made  in  combating  wear  and  dust.     Con- 
firming the  resolutions  passed  at  the  Paris  Congress  in 
1908,  and  in  further  reference  to  the  first  resolution  just 
adopted  which  is  of  interest  not  only  from  the  point  of  view 
of  combating  wear  and  dust  but  from  that  of  binding  the 
materials  in  metalled  roads,  the  Congress  believes: 

a.  That  superficial  tarring  may  be  considered  as  defi- 

nitely accepted  in  practice  and  that  the  advan- 
tage to  be  derived  from  spreading  fine  sand  or 
suitable  stony  material  after  tarring  and  rolling 
the  same  is  not  at  present  proved  and  should  be 
the  subject  of  comparative  tests; 

b.  That  in  the  future  applications  of  these  methods 

the  attention  of  road  builders  should  be  drawn  to 
the  comparison  of  results  obtained  by  the  laying 
of  bituminous  substances,  hot  or  cold,  by  machine 
or  by  hand,  both  from  the  point  of  view  of  cost 
and  from  the  point  of  view  of  the  efficiency  of 
the  operation; 

c.  That  it  is  desirable,  in  comparing  results,  to  take 

into  account  the  quality  of  the  materials  com- 
posing the  metalling,  the  intensity  of  traffic,  and 
tonnage  as  well  as  the  climate; 

d.  That,   with  due  regard  to  the  resources  of  each 

region  in  bituminous  substances,  it  is  important 
to  specify  in  contracts,  the  conditions  that  are  to 


234  HIGHWAY  ENGINEERING 

be  fulfilled,  especially  as  regards  the  preservation 
of  "life,"  that  is  to  say,  the  property  of  preserving 
the  binding  power; 

e.  That  it  would  be  desirable  to  establish  a  comparison 

between  the  advantages  of  tarring,  this  word  be- 
ing taken  in  its  broadest  sense,  under  different 
conditions,  that  is,  whether  the  operations  are  to 
be  frequently  repeated,  small  amounts  being  ap- 
plied each  time,  or  whether  large  quantities  are  to 
be  applied  at  longer  intervals,  and  furthermore 
whether,  or  not,  a  bituminous  substance  has  been 
incorporated  in  the  metalling; 

f.  That  the  conclusion  adopted  by  the  first  Congress 

is  to  be  maintained  "in  toto"  as  follows:  emul- 
sions of  tar  and  of  oil,  hydroscopic  salts,  etc., 
.  .  .  have  a  real  but  not  a  lasting  efficiency. 
Therefore,  their  use  should  be  limited  to  special 
cases,  such  as  race  courses,  festivals,  processions, 
etc. 

Second  Question 

FOUNDATION   AND   DRAINAGE   OF   ROADS.     METHODS 
OF  CARRYING  OUT  THE  WORK. 

Foundation 

1.  The  strength  of   road  foundations  should   be   in- 
creased in  proportion  as  the  supporting  power  of  the  ground 
decreases.     The  foundation  should  have  more  body  and  re- 
sistance, the  more  it  is  exposed  to  internal  deterioration 
and  external  wear. 

2.  In  the  choice  of  the  system  of  foundation  for  both 
stone  block  pavements  and  metalled  roads,  due  considera- 


CONCLUSIONS   OF   THE    SECOND   CONGRESS  235 

tion  should  be  given  to  the  condition  of  the  subsoils,  with 
regard  to  the  possibility  of  their  drainage,  to  their  geo- 
logical nature  and  to  the  nature  of  the  materials  of  the 
locality.  In  order  to  determine  the  thickness  and  the  ex- 
tent of  the  foundations,  the  pressure  per  unit  area  should 
be  made  compatible  with  the  carrying  resistance  of  the 
soils,  observed  under  the  most  unfavorable  conditions. 

Drainage 

3.  In  soils  where  preliminary  drainage  is  required  be- 
fore  the   construction,   the  general  methods   of   drainage 
should  be  applied  to  the  whole  or  to  a  part  of  the  road-bed 
and  to  the  bed  of  the  metal,  if  necessary. 

4.  The  cross  and  longitudinal  sections  of  roads  and  those 
of  side-gutters  should  be  so  established  as  to  facilitate  the 
flow  of  water,  and  to  prevent  infiltration  of  water  into  road 
surfaces,  which  should  be  made  as  impermeable  as  possible. 
The   evaporation  of  superficial  dampness   should  be  en- 
couraged by  every  means. 

5.  The  works  for   the  foundation   and  for   drainage 
should  be  carried  out  simply  and  economically  and  by  using 
the  materials  of  the  locality  as  far  as  possible. 

Third  Question 

LAYING  LIGHT  RAILWAYS  AND  TRAMWAYS  ON  ROADS. 
ADVANTAGES  AND  DISADVANTAGES.  EFFECT  OF  THE  VAR- 
IOUS METHODS  AND  THE  COST  OF  MAINTENANCE. 

1.  In  the  study  of  the  new  roads  to  be  constructed 
both  in  the  neighborhood  of  large  towns  as  well  as  in  the 
open  country,  it  may  be  useful  to  try,  if  it  does  not  interfere 
with  the  public  interest,  to  provide  a  sufficient  road  width 


236  HIGHWAY  ENGINEERING 

for  the  construction  of  a  light  railway  outside  of  the  road- 
way. The  alignment,  gradients  and  the  cross-sections 
should  be  so  designed  as  to  provide  an  economical  and 
efficient  railway  and  also  provide  for  the  safety  of  every 
kind  of  traffic.  It  is  desirable  that  the  cost  of  the  right  of 
way  of  that  part  of  the  road  reserved  for  the  rail  track 
should  be  defrayed  by  the  concession  holder  or  the  con- 
structor of  the  light  railway. 

2.  The  construction  of  sunken  rails  in  the  metalled 
roadways  is  always  detrimental  to  the  life  of  the  roads, 
and  there  also  results  a  marked  increase  in  cost  of  the  main- 
tenance of  the  roads.     It  is  desirable  that  this  method 
should  be  avoided  as  much  as  possible.     The  establishment 
of  rails  for  tramways  in  paved  roads  makes  the  repair  of  the 
paving  abutting  against  the  rails  very  difficult.  It  is  nec- 
essary to  diminish  that  nuisance,  as  far  as  possible,  by 
appropriate  methods. 

3.  Where  the  railway  is  placed  by  the  side  of  the  road 
it  is  preferable,  where  the  width  of  the  road  permits,  to 
construct  it  on  a  special  track,  inaccessible  for  traffic,  and 
superelevated  in  order  to  allow  greater  safety.     In  all  cases 
it  is  necessary  to  provide  proper  drainage.     In  the  case  of 
metalled  roadways,  the  concessionary  or  constructor  of  the 
railway  should  be  obliged  to  construct  on  the  outside  border 
of  the  free  roadside,  sufficient  depots  for  materials  for  the 
repair  of  the  road.     The  same  obligation  should  be,  in  some 
cases,  applied  to  railways  on  paved  roads. 

4.  The  removal  of  trees  along  roadsides  should  not  be 
tolerated,  except  in  extraordinary  cases.     If  the  width  be- 
tween the  tree  rows  is  insufficient  for  the  rail  track  to  allow 
the  recognized  necessary  width  for  ordinary  wheel  traffic,^ 
the  track  should  be  laid  on  the  outside  of  the  trees. 


CONCLUSIONS   OF   THE    SECOND   CONGRESS  237 

5.  It  is  desirable  that  the  concessionary  of  light  rail- 
ways should  undertake  the  duty  of  maintaining  the  area 
of  the  road  or  roadway  occupied  by  the  rails  or  contiguous 
to  same,  and  pay  the  costs  of  this  maintenance. 

Fourth  Question 

CLEANSING  AND  WATERING.  NECESSITY  OR  UTILITY. 
METHODS  IN  USE.  THEIR  COST.  COMPARISON  OF  VARIOUS 
METHODS. 

1.  Throwing  refuse  upon  the  public  roads  should  be 
carefully  avoided.     Such  refuse  should  be  swept  up  and 
removed  by  the  municipality  and  not  by  the  owners  of 
adjoining  property,  provided  the  cost  of  this  work  is  re- 
covered from  the  latter  by  taxation. 

2.  In  large  towns  it  is  necessary  to  give  special  care  to 
cleansing    and    watering.     Cleansing    should    be    done    as 
rapidly  as  possible.     Watering  must  be  frequent,  and  limited 
in  amount  depending  on  local  conditions.     Washing  and 
sweeping  are  to  be  done  as  early  as  possible.     Mechanical 
processes  are  particularly  recommended. 

3.  Improvement   in  the   machines    are  to   be  sought 
for  with  a  view  of  insuring  the  most  complete,  cleansing 
with  the  least  inconvenience  to  the  public.     Motor  machines 
can  be  advantageously  used  for  cleaning  and  road  watering 
in  large  towns. 

Fifth  Question 
CHOICE  OF  SURFACING  MATERIALS. 

1.  Macadam,  constructed  according  to  the  methods  of 
Tresaguet  and  Me  Adam,  causes  dust  and  mud,  is  expensive 
to  maintain,  and  is  only  suitable  in  large  cities  for  streets 
where  the  traffic  is  not  very  great  or  heavy. 


238  HIGHWAY   ENGINEERING 

2.  The  experimental  work  carried  out  in  recent  years 
with  macadam  improved  by  using  a  bituminous  binder 
should  be  continued  in  order  to  determine  the  best  methods 
of  utilizing  this  kind  of  construction  under  varying  con- 
ditions, so  that  this  question  may  be  submitted  again  at 
the  next  Congress. 

3.  Stone  pavement  has  great  qualities  of  resistance  and 
durability.     Its  maintenance  is  easy  and  economical,   it 
produces  practically  no  dust,  and  is  suitable  where  there 
are  tramway  tracks. 

4.  Stone   pavement  should  be  adopted  in  thorough- 
fares, wherever  noise  is  of  little  consequence,  or  when  wood 
or  asphalt  surfaces  are  not  suitable.     It  should  consist  of 
blocks  which  are  regular  in  shape,  durable  but  not  slippery, 
and  will  wear  evenly.     The  blocks  should  be  laid  with  close 
joints  upon  a  foundation. 

5.  The  Congress  expresses  the  wish  to  see  the  trials  of 
small  block  pavements  continued  wherever  local  circum- 
stances and  traffic  conditions  permit. 

6.  Wood  paving  is  noiseless,  is  not  slippery  if  kept 
clean  and  stands  very  heavy  traffic.     The  use  of  it  should 
be  extended  even  to  thoroughfares  through  which  tramway 
lines  run. 

7.  The  respective  advantages  of  soft  and  hard  wood 
blocks  must  be  a  subject  of  discussion  at  a  forthcoming 
Congress. 

8.  Asphalt  pavements  should  be  recommended,  owing 
to  their  good  qualities  from  the  hygienic  point  of  view,  their 
ease  of  cleansing  and  of   repair,  and  the    small    tractive 
effort  required  on  them.     This  surfacing  is  almost  noiseless 
and  produces  but  little  dust,  but  it  is  unsatisfactory  adjacent 
to  tramway  rails. 


CONCLUSIONS   OF   THE    SECOND    CONGRESS  239 

9.  There  is  opportunity  for  its  use  in  fashionable 
thoroughfares  where  the  traffic  is  not  severe,  where  there 
are  no  tramways,  and  where  the  gradients  are  very  moderate. 
10.  Finally,  the  trials  of  asphalt  flag  and  block  pave- 
ments should  be  continued  with  regard  to  those  qualities 
not  yet  determined. 

Sixth  Question 

METHODS  OF  CARRYING  OUT  ROAD  WORK  IN  CONNEC- 
TION WITH  LIGHTING  AND  WATER  SUPPLY. 

1.  It  is  desirable  to  free  as  far  as  possible  the  carriage- 
way from  the  minor  distribution  systems  which  now  en- 
cumber them,  and  to  leave  in  them  only  the  large  sewers  and 
mains  which  require  little  attention. 

2.  As   far   as   possible   the   minor   distribution   mains 
which  are  connected  to  the  adjoining  houses  should  be 
doubled   and   placed   on   both   sides   of   the   street.     This 
doubling  is  especially  recommended  for  streets  with  heavy 
traffic  and  also  for  those  where  the  surface  rests  on  a  solid 
foundation. 

3.  It  is  advisable  to  consider  the  advantages  of  placing 
all  distribution  systems,  except  gas,  in  subways  of  suitable 
dimensions  placed  under  the  footways.     In  this  case  great 
care  must  be  taken  to  prevent  flooding  caused  by  breakage 
of  water  pipes. 

4.  When  the  distribution  works  have  been  placed  under 
the   carriageway,    the   Congress   advises   that   the   double 
system  should  be  gradually  adopted  by  taking  advantage 
of  the  opportunity  given  by  considerable  repairs  or  altera- 
tions. 

5.  Complete  agreement  is  necessary  between  all  author- 
ities interested  in  the  streets,  in  order  to  conduct  their 


240  HIGHWAY  ENGINEERING 

operations  so  as  to  interfere  as  little  as  possible  with  the 
traffic.  It  is  most  desirable  that  all  street  works  should  be 
under  the  general  direction  of  those  responsible  for  maintain- 
ing the  surface.  The  work  must  be  carried  out  as  rapidly 
as  possible  so  as  to  reduce  both  the  space  occupied  on  the 
public  highway  and  the  obstructions  to  traffic  to  a  minimum. 
6.  Trees,  planted  in  the  footways  in  urban  districts, 
should  be  selected  so  as  not  to  inconvenience  the  property 
owners  by  their  leaves  nor  interfere  with  the  distribution 
systems  by  their  roots. 

Seventh  Question 

INFLUENCE  OF  WEIGHT  AND  SPEED  OF  VEHICLES  ON 
BRIDGES  AND  OTHER  SPECIAL  STRUCTURES. 

1.  The  development  of  mechanical  traffic  has  not  up 
to  the  present  increased  the  weight  of  vehicles  beyond  the 
limits  recognized  by  specifications  in  connection  with  bridge 
design.     In  any  case  it   is  desirable  that,  when  existing 
specifications  are   revised,  steps  should  be  taken  to  test 
bridges  by  placing  upon  them  under  the  most  unfavorable 
conditions,  the  heaviest  probable  loads,  composed  exclusively 
of  mechanical  vehicles. 

2.  Under  the  present  conditions  of  constructing  motor 
vehicles  and  building  public  roads  it  does  not  seem  possible 
that  the  speed  of  vehicles  could  have  any  effect  on  modern 
and  well  built  bridges  which  has  not  already  been  duly 
taken  into  account  by  the  usual  methods  of  calculations  of 
strength.     It  may  be  advisable,  however,  when  testing  new 
bridges  or  retesting  existing  bridges  to  make   use   of  the 
heaviest  motor  driven  vehicles  running  at  high  speed. 

3.  The  consolidation  of  the  different  parts  of  which 


CONCLUSIONS   OF  THE   SECOND   CONGRESS  241 

bridges  are  composed  aid  their  capacity  to  withstand  the 
effects  of  vehicular  traffic. 

Eighth  Question 

ROAD  VEHICLES.  CONDITIONS  TO  BE  FULFILLED  BY 
HORSE  OR  MECHANICALLY  DRIVEN  VEHICLES  IN  ORDER 
THAT  THEY  MAY  NEITHER  CAUSE  NOR  SUFFER  ANY  EXTRA- 
ORDINARY DAMAGE  TO  OR  FROM  THE  ROADS. 

1.  With  regard  to  animal  drawn  vehicles: 

a.  Heavily   loaded   vehicles   with   narrow   tires   may 

cause  exceptional  damage  to  roads  constructed 
for  general  traffic. 

b.  It  is  desirable  that  trials  be  undertaken  for  the 

purpose  of  determining  the  relation  which  should 
exist  between  the  load,  the  diameter  of  wheel,  and 
the  width  of  tire  so  as  to  avoid  abnormal  damage. 

2.  With  regard  to  mechanically  driven  vehicles: 

a.  Automobiles  of  the  touring  car  type  cannot  cause 

abnormal  damage  to  the  roads  as  long  as  their 
speed  is  kept  within  limits; 

b.  Public  service  automobiles  cannot  cause  appreciable 

damage  to  the  road  provided  that  the  maximum 
speed  does  not  exceed  25  kilom.  per  hour,  the 
maximum  axle-load  does  not  reach  4  tonnes  on 
the  heaviest  axle  and  that  with  wheels  of  1  meter 
diameter  the  load  is  below  150  kilog.  per  centi- 
meter width  of  tread. 

c.  Industrial  automobiles  need  not  cause  exceptional 

damage  to  a  well  constructed  road  provided  that 
the  following  limits  are  adhered  to: 
First  type:  vehicles  in  which  the  axle-load  is  less  than 
tonnes: 


242  HIGHWAY   ENGINEERING 

Maximum  speed:  20  kilom.  per  hour. 

Load  on  tires:  150  kilog.  per  centimeter  of  width  of 
tire  with  wheels  of  1  meter  in  diameter. 

In  the  narrow  streets  in  towns  and  large  cities  when 
vibrations  of  the  ground  are  to  be  feared,  it  is 
possible  to  minimize  the  inconvenience  by  reducing 
the  speed  in  suitable  proportion. 

Second  type:  vehicles  in  which  the  maximum  axle- 
loads  are  between  4}^  and  7  tonnes: 

Maximum  speed:    12  kilom.  per  hour. 

Load  on  tires:  150  kilog.  per  centimeter  of  width  of 
tire  with  wheels  of  1  meter  in  diameter. 

Provisionally,  while  awaiting  the  results  of  further 
experiments,  when  the  diameter  of  the  wheels  is 
above  1  meter,  the  load  per  centimeter  width  of 
tire  should  be  calculated,  for  both  types  of  vehi- 
cles and  also  for  such  as  are  described  in  para- 
graph 2,  by  using  the  formula 

C  =  150  Vd 

where  d  =  diameter  in  meters  and  C  =  the  load  in 
kilograms. 

It  is  desirable  that  experiments  should  be  undertaken 
in  order  to  determine  the  maximum  width  which 
can  be  given  to  the  tires  of  all  automobiles  while 
still  insuring,  under  normal  conditions,  that  the 
distribution  of  the  load  on  the  ground  should  take 
place  over  the  whole  carrying  area. 

d.  Ribbed  or  grooved  iron  tires  cause  abnormal  damage 

to  the  road   independent  of   their  width  or  the 
load  they  support. 

e.  Vehicles    propelled    by    mechanical    power    cannot 


CONCLUSIONS   OF   THE    SECOND    CONGRESS  243 

cause  extraordinary  damage  to  the  curved  por- 
tions of  roads  provided  that  at  these  points  a 
sufficient  super-elevation  is  given  and  that  the 
curved  portion  is  not  approached  or  traversed  at 
an  unreasonable  speed. 

f.  With  a  view  to  saving  the  roads,  it  is  desirable  that 
the  car  builders  go  carefully  into  the  question  of 
clutches  and  brakes  so  that  the  skidding  of  the 
wheels  may  be  avoided;  that  they  also  balance 
the  motors  as  perfectly  as  possible;  and  that  they 
allow  a  reasonable  raising  of  the  center  of  gravity. 

Ninth  Question 

CONDITIONS  FOR  THE  USE  OF  PUBLIC  SERVICE    CON- 
VEYANCES    OTHER     THAN     TRAMWAYS.       ADVANTAGES     AND 

DISADVANTAGES,  CAPACITY,  COST,  ETC. 

1.  The  Congress  is  of  the  opinion  that  public  motor 
omnibus  service  should  be  encouraged. 

2.  As  a  final  resolution,  the  Congress  is  of  the  opinion 
that  it  is  difficult  at  the  present  moment  to  decide  definitely 
on  the  respective  advantages  of  the  two  modes  of  transport 
but  that  one  forms  the  complement  of  the  other  and  not 
the  rival,  and  the  adoption  of  one  or  the  other  method 
largely  depends  on  local  conditions. 

3.  The  progress  of  the  motor  omnibus  and  extent  of 
the  use  of  this  method  of  transportation  is  capable  of  great 
extension : 

a.  By  the  use  of  wheels  fitted  with  rubber  tires. 

b.  By  any  progress  made  in  construction. 

4.  The  number  of  passengers  carried  by  motor  omni- 
buses should  be  greater  for  the  town  than  for  the  country. 


APPENDIX  I 

PROCEEDINGS  OF  THE  PERMANENT  INTERNATIONAL 
COMMISSION 

A  meeting  of  the  Permanent  International  Commission 
of  the  Association  was  held  at  Brussels  on  July  31st,  1910. 
It  was  attended  by  forty-four  members  representing  eighteen 
countries. 

M.  Mahieu,  Secretary-General  of  the  Association, 
announced  that  M.  Lethier,  President  of  the  Association, 
was  prevented  from  attending  the  meeting  by  illness. 
M.  de  Preaudeau,  Vice-President  of  the  General  Council 
of  Bridges  and  Roads  of  France,  upon  unanimous  request, 
acted  as  President. 

M.  Mahieu  stated  that  twenty-six  governments  were 
affiliated  with  the  Association  and  that  the  number  of 
permanent  members  had  now  reached  723. 

It  was  announced  that  the  Executive  Bureau  was 
occupied  with  the  establishment  of  a  library  which  would 
include  all  literature  concerning  roads  published  throughout 
the  world.  Although  it  is  expected  that  many  books,  reports 
and  other  publications  will  be  furnished  gratuitously,  the 
budget  provides  for  an  expenditure  of  200  dollars  for  ad- 
ditions to  the  library. 

M.  Mahieu  also  reported  on  the  foundation  for  a 
Laboratory.  Arrangements  have  been  completed  with  the 
Minister  of  Finance  of  the  Department  of  Public  Works  of 
France  by  which  the  Association  will  have  the  use  of  the 
Laboratory  of  the  National  School  of  Bridges  and  Roads 

244 


APPENDIX  I  245 

by  the  annual  payment  of  600  dollars.  The  following 
regulations  have  been  drawn  up  covering  the  administration 
of  the  Laboratory. 

Article  1.  The  Permanent  International  Commission 
shall  determine  each  year  the  nature  and  the  extent  of  the 
research  work  of  the  Laboratory  which  the  Executive 
Bureau  is*  authorized  to  undertake  during  that  period. 

Article  2.  The  substances  required  for  the  research 
work  and  the  necessary  analyses  will  be  collected  by  the 
Executive  Bureau. 

The  results  of  the  research  work  of  the  Laboratory 
shall  be  the  exclusive  property  of  the  Association :  they  will 
be  sent  to  all  the  Members  of  the  Association,  in  the  form  of 
an  annual  report  of  the  Executive  Office,  with  a  simple 
indication  of  the  source  of  origin.  The  names  of  the  sup- 
pliers of  the  samples  shall  only  be  published  with  their 
written  consent. 

Article  3.  The  report  shall  not  contain  any  criticism  on 
the  relative  value  of  the  various  products  analysed  or  ex- 
perimented with. 

Article  4.  No  paid  analyses  for  third  parties,  even  if 
members  of  the  Association,  will  be  made  by  the  Executive 
Bureau. 

Articles  6  and  17  of  the  Regulations  of  the  Association 
were  modified  so  as  to  read  as  follows: 

Article  6  (last  paragraph):  "It  shall  administer  the 
Funds  of  the  Association  and  invest  them  in  bonds  of  the 
French  Government,  in  Debentures  of  the  Railways  guaran- 
teed by  the  French  State,  or  in  Debentures  of  the  Premium 
Bonds  of  the  Credit  Foncier  de  France  and  of  the  City  of 
Paris.  It  shall  represent  the  Association  in  all  judiciary 
actions." 


246  HIGHWAY   ENGINEERING 

Article  17  (first  paragraph):  "The  discussions  at  a 
plenary  meeting  or  sectional  meeting  shall  take  place  in 
the  languages  accepted  by  the  Congress  and,  according  to 
circumstamces,  in  the  language  of  the  country  where  the 
Congress  is  being  held.  The  speakers,  however,  are  author- 
ized to  use  their  own  language  under  the  express  condition 
of  translating  or  causing  to  be  translated  the  words  spoken 
into  one  of  the  three  accepted  languages  of  the  Congress. 
This  translation  will  appear  in  the  transactions  provided 
for  under  Article  20,  and  the  original  speech  will  only  be 
mentioned  as  having  taken  place. " 

The  following  very  important  resolution  was  adopted 
by  the  Commission  and  hence  will  apply  to  the  regulations 
governing  the  1913  Congress. 

"That  the  reports  be  restricted  to  one  report  per 
country  on  one  given  subject,  it  being  understood,  however, 
that  Governments,  Corporate  Bodies,  and  private  individ- 
uals shall  always  have  the  right  of  defraying  personally  the 
costs  of  supplementary  reports  which  they  think  should  be 
published  on  any  question  which  interests  them  in  a  par- 
ticular manner." 


APPENDIX  II 


REGULATIONS    OF    THE    PERMANENT    INTERNATIONAL 
ASSOCIATION  OF  ROAD  CONGRESSES 

Approved  by  the  Permanent  International  Association  in 
its  meeting  of  the  29th  of  March,  1909 

1.  Object  and  Organization  of  the  Association  ' 

ARTICLE  1 

The  object  of  the  Permanent  International  Association 
of  Road  Congresses  is  to  promote  progress  in  the  construc- 
tion, traffic  and  exploitation  of  roads. 

It  continues  the  work  of  the  first  International  Road 
Congress  held  in  Paris,  in  October,  1908. 

It  accomplishes  its  object: 

1st.  By  organizing  Road  Congresses : 

2d.  By  publishing  Papers,  Proceedings,  and  other 
Documents; 

3d.  By  collecting  the  results  of:  (a)  Tests  carried  out 
on  roads;  (b)  Laboratory  tests  throughout  the  world  on 
materials  which  are  used  or  are  suitable  for  road  construc- 
tion and  maintenance;  these  tests  may  be  either  in  the 
form  of  mere  records  collected  by  the  Association  or  they 
may  have  been  carried  out  by  the  Association  itself  or 
through  its  instrumentality. 

Its  affairs  are  managed  by  a  Permanent  International 
Commission. 

247 


248  HIGHWAY  ENGINEERING 

ARTICLE  2 

The  Association  consists  of: 

1st.  Delegates  of  Governments  and  Corporations  of 
all  the  countries  which  subscribe  annually  to  the  Association. 

The  term  Corporation  includes:  Public  departments, 
Provincial  Governments,  County,  District,  Communal  and 
Municipal  Bodies,  Chambers  of  Commerce,  Scientific  or 
Technical  Institutions,  Tourist  and  Sporting  Clubs,  Pro- 
fessional Associations  or  Trade  Unions,  Transport  Com- 
panies, Agricultural,  Industrial  and  Commercial  Societies 
or  Companies,  etc. 

2d.  Private  Members. 

Membership  may  be  either  permanent  or  temporary. 

Governments  may  appoint  one  official  delegate,  with 
a  right  to  vote  at  every  Congress,  for  each  50  dollars  of  their 
annual  subsidy. 

This  amount  is  reduced  to  20  dollars  for  Corporations. 

Permanent  Members  are  entitled  to  attend  and  vote  at 
every  Congress. 

Temporary  Members  are  entitled  to  attend  the  par- 
ticular Congress  they  have  joined,  and  they  may  vote  on 
all  questions  which  do  not  affect  the  Permanent  Association 
itself. 

3d.  Honorary  Members,  nominated  by  the  Permanent 
International  Commission. 

ARTICLE  3 

1st.  A  Permanent  International  Commission,  with 
headquarters  at  Paris,  is  at  the  head  of  the  Association. 

2d.  A  Permanent  Council  and  an  Executive  Committee 
are  appointed  from  amongst  the  Members  of  this  Com- 
mission. 


APPENDIX   II  249 

ARTICLE  4 

The  Permanent  International  Commission  is  composed 
of  members  belonging  to  the  various  countries  represented 
in  the  Association.  Each  country  has  the  right  to  one 
representative  for  each  200  dollars  of  its  total  annual  sub- 
sidy. 

Provided,  however,  that  the  number  of  representatives 
from  any  one  country  shall  not  exceed  15  (fifteen),  and  that 
any  country  which  pays  not  less  than  50  dollars  shall  have 
the  right  to  appoint  one  delegate. 

Furthermore,  the  General  Presidents  and  the  General 
Secretaries  of  the  Road  Congresses  are  ex-officio  Members  of 
the  Permanent  Commission. 

At  the  head  of  the  Permanent  Commission  there  is  a 
President,  a  Vice-President  and  a  General  Secretary  who 
together  constitute  the  Executive  Committee. 

This  Commission: 

1st.  Determines  when  and  where  the  first  Congress 
shall  be  held. 

2d.  Arranges  at  the  proper  time  for  the  formation  of  a 
Local  Organizing  Commission  at  the  place  selected  for  the 
Congress. 

3d.  After  consultation  with  the  Local  Organizing  Com- 
mission, determines  the  languages  which  shall  be  officially 
recognized  by  the  Congress;  prepares  the  Agenda  and 
settles  the  questions  to  be  submitted  to  the  Congress  as  also 
the  nature  and  number  of  the  communications  it  shall  deal 
with;  arranges  the  business  of  the  Meetings;  and  appoints 
the  writers  of  Papers  on  the  several  questions. 

4th.  Supports,  when  necessary,  the  Local  Commission 
in  its  application  to  foreign  Governments. 


250  HIGHWAY  ENGINEERING 

5th.  Approves  the  estimates  of  expenses  to  be  defrayed 
out  of  the  permanent  funds  of  the  Association;  supervises 
the  financial  management;  and  decides,  generally,  upon  all 
the  administrative  measures  which  it  considers  may  promote 
the  work  of  the  Congress. 

6th.  Nominates  Honorary  Members. 

The  Commission  meets  whenever  it  is  convened  by  the 
Executive  Committee,  or  upon  the  written  requisition  of  a 
quarter  of  its  Members  addressed  to  the  President  of  the 
Executive  Committee,  and,  at  any  rate,  at  the  time  of  the 
Congress  Sessions. 

The  Members  of  the  Permanent  Commission,  who  do 
not  find  it  possible  to  attend  a  meeting,  may  delegate  their 
powers  to  one  of  the  Members  of  the  Commission. 

ARTICLE  5 

The  Permanent  Council  is  composed  of  representatives 
chosen  from  among  the  members  of  the  Permanent  Com- 
mission, namely: 

One  for  each  country  whose  annual  subsidy  does  not 
exceed  1000  dollars; 

Two  for  each  country  whose  annual  subsidy  exceeds 
this  amount,  and  is  less  than  2000  dollars. 

Three  for  each  country  whose  annual  subsidy  exceeds 
2000  dollars. 

The  President,  Vice-President  and  General  Secretary 
of  the  Permanent  Commission  are  at  the  head  of  the  Per- 
manent Council. 

The  Permanent  Council: 

1st.  Carries  out  the  resolutions  of  the  International 
Commission,  and  decides  upon  all  questions  not  expressly 
reserved  for  the  decision  of  the  Commission. 


APPENDIX   II  251 

2d.  Decides  upon  the  admission  of  Corporations  and 
Permanent  Members  referred  to  in  Article  2. 

3d.  Draws  up  the  estimates  to  be  defrayed  out  of  the 
permanent  funds  of  the  Association,  and  assists  and  controls 
the  Executive  Committee. 

4th.  After  having  requested  proposals  from  the  Local 
Commission  the  Council  proceeds  to  appoint  the  General 
Committee  and  Sectional  Committees  of  the  next  Congress, 
appointing  as  Vice-Presidents  on  each  Committee  three 
Members  of  the  Permanent  Commission  who  are  familiar, 
as  far  as  possible,  with  the  languages  officially  recognized 
by  the  Congress,  and  it  also  appoints  Secretaries  who  are 
well  versed  in  these  languages. 

5th.  The  Council  meets  whenever  convened  by  the 
Executive  Committee,  or  upon  the  request  of  one-fourth  of 
its  Members  addressed  to  the  President  of  the  Executive 
Committee. 

ARTICLE  6 

The  Executive  Committee,  as  stated  under  Article  4, 
is  composed  of  the  President,  Vice-President  and  General 
Secretary  of  the  Permanent  Commission  and  of  the  Per- 
manent Council.  In  addition  to  an  Accountant,  it  may 
appoint  Secretaries  who  shall  be  specially  entrusted  with  the 
translations  and  a  Secretary  who  shall  have  special  charge 
of  the  head  office  for  laboratory  experiments  on  materials 
used  in  the  construction  and  maintenance  of  roads. 

The  Members  of  the  Executive  Committee  shall  belong 
to  the  country  in  which  the  headquarters  of  the  Permanent 
Commission  are  situated. 

It  collects  the  records  of  experiments  carried  out  on 
roads  throughout  the  whole  world  and  the  records  of  labora- 


252  HIGHWAY  ENGINEERING 

tory  tests  in  all  countries  on  materials  used  in  the  construction 
and  maintenance  of  roads;  it  arranges  for  fresh  experiments 
to  be  carried  out  and  if  necessary  carries  them  out  itself. 

It  is  specially  concerned  in  specifying  the  conditions 
which  shall  be  complied  with  by  all  those  materials,  whatever 
their  nature,  such  as  tars,  mineral  oils  and  other  kindred 
products,  which  are  used  or  can  be  used  practically  in  the 
construction  and  maintenance  of  roads. 

It  attends  to  the  despatch  of  current  business,  keeps  the 
accounts,  prepares  the  estimates  of  expenses  to  be  defrayed 
out  of  the  permanent  funds  of  the  Association,  keeps  the 
expenses  within  the  limits  of  the  approved  estimates,  signs 
checks,  and  collects  subscriptions  and  all  other  money  due 
to  the  Association. 

It  deals  with  all  investigations,  tests,  and  occasional  or 
periodical  publications  decided  upon  by  the  Permanent 
Council  or  by  the  Permanent  Commission. 

It  has  charge  of  the  library,  archives,  documents  and 
accounts. 

It  translates,  when  necessary,  publishes  and  transmits 
to  the  Members  of  the  Congress,  the  papers,  communications 
and  proceedings  of  the  Congress. 

It  handles  the  funds  of  the  Association  and  invests  them 
in  French  Government  securities  or  in  French  railway 
debentures  guaranteed  by  the  State  and  represents  the 
Association  in  legal  proceedings. 

ARTICLE  7 

The  representatives  of  the  various  countries,  both  on 
the  Permanent  Commission  as  well  as  on  the  Permanent 
Council,  are  appointed  by  the  Governments  of  the  respective 
countries  in  the  proportions  stated  in  Articles  4  and  5. 


APPENDIX   II  253 

It  devolves  upon  the  Government  of  each  country, 
whenever  occasion  arises,  to  fill  vacancies  which  may  occur 
amongst  their  representatives  on  the  Commission  or  on  the 
Permanent  Council,  through  death  or  through  the  expiry  of 
their  term  of  office. 

ARTICLE  8 

Each  Congress  entails  the  appointment  of  a  Local 
Organizing  Commission  which  includes  the  local  Members 
of  the  Permanent  Commission  and  holds  office  till  the  close 
of  the  Congress. 

This  Commission  includes  committees  of  patronage, 
administration,  reception,  excursion,  and  others. 

It  undertakes  the  propaganda  in  the  country  where -the 
Congress  is  to  be  held,  and,  in  accord  with  the  Permanent 
Council,  selects  persons  in  that  country  for  Presidents  and 
Members  of  the  Committee  and  Sectional  Committees  of  the 
Congress. 

It  draws  up,  in  consultation  with  the  Permanent  Council, 
the  detailed  program  of  the  Meetings,  and  distributes  it  to 
all  the  Members  of  the  Congress  at  the  opening  of  the 
Session. 

It  organizes  the  various  excursions,  receptions,  and  fetes. 

It  provides  the  rooms  in  which  the  Meetings  are  held. 

It  advises  the  Permanent  Commission  on  the  languages 
which  may  be  officially  recognized  by  the  Congress  and  on 
the  translations  which  have  to  be  made  for  the  Session;  the 
language  of  the  country  in  which  the  Congress  is  held,  will 
have  to  be  admitted,  if  required  by  the  Local  Commission. 

It  organizes  the  service  of  correspondence,  lodgings, 
interpreters,  and  helps  where  necessary  the  Permanent 
Commission  in  arranging  at  the  expense  of  the  Association 


254  HIGHWAY   ENGINEERING 

for  the  translation  and  printing  into  the  language  of  the 
country  where  the  Congress  is  held,  of  Papers  which  have 
been  written  in  any  of  the  other  languages  officially  recog- 
nized by  the  Congress. 

Conversely  it  arranges  at  the  expense  of  the  Association 
for  the  translation,  into  any  of  the  other  languages  recognized 
by  the  Congress,  of  Papers  which  have  been  written  in  the 
language  of  the  country  where  the  Congress  is  held. 

It  puts  the  Permanent  Commission  into  touch  with  the 
local  authorities. 

It  presides  over  and  conducts  the  Session  of  the  Con- 
gress. 

It  defrays  the  expense  of  the  Congress  by  means  of  the 
subscriptions  of  the  temporary  members,  fixed  at  five  dollars, 
by  other  special  grants,  and,  if  required,  by  a  subsidy  from 
the  Association. 

It  keeps  a  special  account  of  the  expenditure  of  the 
subsidy  which  may  be  granted  by  the  Association,  and  it 
may  not,  without  the  authority  of  the  Executive  Committee, 
incur  any  expense  on  behalf  of  the  Association,  beyond  the 
aforesaid  subsidy. 

ARTICLE  9 

The  permanent  funds  of  the  Association  are  derived 
from: 

1st.  The  annual  grants  from  Governments  and  Corpora- 
tions. 

2d.  The  subscriptions  of  permanent  Members  (see 
Article  2). 

Permanent  membership  involves  a  yearly  subscription 
of  two  dollars.  This  subscription  is  increased  to  five  dollars, 
for  the  first  year,  in  the  case  of  permanent  Members  who  are 


APPENDIX   II  255 

enrolled  during  a  Congress  year.  Permanent  Members  may 
pay  in  the  fees  of  three  consecutive  years  at  once.  Honorary 
Members  pay  no  subscriptions. 

3d.  Various  donations  and  gifts. 

ARTICLE  10 

1st.  The  financial  year  commences  on  the  first  day  of 
January. 

2d.  Subscriptions  are  payable  as  follows: 

Permanent  Members:  at  the  time  of  enrollment,  and 
on  January  of  each  year,  in  advance,  to  the  Office  of  the 
Executive  Committee. 

Temporary  Members :  at  the  time  of  enrollment,  to  the 
Office  of  the  Local  Organizing  Commission. 

The  expenses  of  collection  must  be  borne  by  the  Mem- 
bers. 

Special  subscriptions  may  be  solicited  by  the  Local 
Organizing  Commission  from  the  Members  who  take  part 
in  the  excursions  and  fetes  during  the  Congress.  Participa- 
tion in  these  is  optional,  and  the  number  of  the  participants 
may  be  limited. 

ARTICLE  11 

Every  Member  is  entitled: 

1st.  To  take  part  in  the  Meetings  of  the  Congress  and 
to  vote  upon  all  questions  submitted. 

2d.  To  receive  the  publications  of  the  Congress,  in  any 
one  of  the  languages  recognized  by  the  Congress,  which  he 
may  select.  The  Association  is  not  bound,  however,  to 
replace  copies  which  are  lost  or  damaged  in  transit. 

Permanent  and  Honorary  Members  are  further 
entitled : 


256  HIGHWAY  ENGINEERING 

(a)  To   lay   before   the  Permanent   Commission   any 
questions  to  be  submitted  to  the  Congress.     Such  questions, 
accompanied  by  a  concise  report  giving  reasons  for  the 
same,  must  reach  the  Commission  at  least  one  year  before 
the  Meeting  of  the  Congress. 

(b)  To  vote  on  all  questions  depending  on  the  Per- 
manent Association  at  the  meetings  of  the  Congress  or  at 
the  special  meetings. 

(c)  To   receive   the   publications   distributed   by   the 
Association  at  other  times  than  during  the  sessions  of  the 
Congress. 

The  number  of  copies  of  publications  sent  to  Govern- 
ments and  Corporations  is  determined  on  the  same  basis 
as  the  right  to  vote.  (Article  2.) 

Each  Government  or  Corporation,  whatever  the 
amount  of  its  contribution,  receives  at  least  one  copy  of 
the  publications. 

II.  Sessions  of  the  Congress 

ARTICLE  12 

The  Permanent  Commission  convenes  the  Congress 
from  time  to  time,  at  intervals  of  about  three  years,  as 
nearly  as  possible. 

ARTICLE  13 

1st.  The  Congress  comprises: 

Two  Sections:  One  for  the  construction  and  mainte- 
nance of  roads  and  the  other  for  traffic  and  exploitation. 

These  Sections  may  be  subdivided. 

2d.  Its  proceedings  consist  of  General  Meetings,  Sec- 
tional Meetings,  Excursions  and  Receptions. 


APPENDIX   II  257 

The  number  and  nature  of  the  questions  to  be  discussed 
by  the  Congress  are  settled  by  the  Permanent  Commission. 
This  Commission  also  settles  the  number  and  nature  of 
communications  which  may  be  submitted  to  the  Congress 
in  addition  to  the  ordinary  program  of  questions. 

As  a  general  rule  each  country  shall  only  furnish  one 
Paper  on  any  given  "  Question "  or  topic  of  a  "  Communica- 
tion." 

ARTICLE  14 

The  Reporter  or  Reporters,  selected  by  the  Commission 
for  any  given  question  or  topic  of  a  communication  and  for 
any  given  country,  shall  collect  in  that  country  all  the  data 
needed  for  the  preparation  of  their  Paper. 

Their  work,  supported  by  conclusions  if  they  deem  these 
desirable,  should  reach  the  Executive  Committee,  at  the 
latest,  eight  months  before  the  opening  of  the  Congress. 

The  Permanent  Commission  appoints  a  General  Re- 
porter for  each  question,  whose  duty  shall  consist  of  sub- 
mitting to  the  Congress  a  short  review  of  the  chief  features 
of  this  question,  together  with  a  summary  of  the  Papers 
which  have  been  transmitted  to  him. 

The  General  Reporter  may  give  his  own  views  and  data, 
and  he  may  arrange  with  the  various  authors  of  Papers  for 
formulating  joint  proposals.  As  far  as  possible,  he  shall 
belong  to  the  country  in  which  the  Congress  is  held. 

ARTICLE  15 

The  Papers  upon  each  "  Question/7  and  also  the 
General  Reports  must  be  forwarded  to  the  Executive 
Committee  within  the  limit  of  time  allowed  to  their  Authors; 


258  HIGHWAY  ENGINEERING 

they  will  be  translated  and  printed  in  the  official  languages 
of  the  Congress. 

The  Papers  must  be  written  in  one  of  the  official  lan- 
guages of  the  Congress  and  should  be  typewritten  if  possible 
on  one  side  of  the  paper  only. 

Each  Paper  should  not  exceed  about  8,000  words,  the 
number  of  illustrations  inserted  in  the  text  should  not 
exceed  6,  and  the  total  surface  occupied  by  them  should 
not  exceed  46.5  square  inches. 

The  plates  separate  from  the  text,  either  drawings  or 
half-tones,  should  not  exceed  two  in  number,  except  in 
special  cases.  Their  size  should  not  exceed  9.4  inches  in 
depth  by  17.7  inches  in  width,  including  the  border  line, 
or  8.7  inches  by  17.0  inches  within  the  border  line. 

The  drawings  should  be  made  in  clear  black  lines  on 
tracing  paper  so  as  to  allow  blocks  to  be  made  from  them  if 
necessary. 

The  "  Communications "  are  not  translated  and  are 
not  submitted  for  discussion  during  the  Session  of  the  Con- 
gress until  after  the  " Questions"  in  the  Agenda  have  been 
dealt  with,  and  then  only  if  time  permits. 

In  addition  to  the  "  Communications  "  referred  to  in 
the  above  articles  13  and  14,  which  are  printed  at  the  ex- 
pense of  the  Association,  the  Permanent  Commission  may 
admit  "  Communications  "  printed  by  their  Authors  at  their 
own  expense;  in  the  latter  case  the  required  number  of 
copies  must  be  supplied  to  the  Executive  Committee  and 
furthermore  they  will  not  be  voted  upon,  nor  brought  up  for 
consideration  at  a  General  Meeting. 

Writers  of  Papers  upon  " Questions"  or  "Communica- 
tions," may,  if  they  wish,  furnish  their  own  translations  into 
the  various  official  languages  of  the  Congress. 


APPENDIX  II  259 

ARTICLE  16 

The  " Questions"  are  first  discussed  at  the  Sectional 
Meetings  and  afterwards  at  a  General  Meeting. 

ARTICLE  17 

1st.  The  discussions,  either  at  General  Meetings  or  at 
Sectional  Meetings,  are  conducted  in  the  languages  officially 
recognized  by  the  Congress,  and  also,  when  required,  in  the 
language  of  the  country  where  the  Congress  is  held. 

2d.  Unless  otherwise  decided  by  the  Meeting,  persons 
taking  part  in  the  discussions  are  not  allowed  to  speak  for 
more  than  ten  minutes,  nor  can  they  address  the  same 
Meeting  more  than  twice  upon  the  same  subject  unless  the 
Meeting,  on  being  consulted,  decides  otherwise. 

3d.  The  discussion  in  Sectional  Meetings  or  in  General 
Meeting  will  be  preceded  for  each  question  by  a  brief  sum- 
mary of  the  reports  by  the  General  Reporter  who  has  been 
appointed  under  the  terms  of  Article  14. 

After  discussing  each  question  submitted  to  it,  each 
Section  may  appoint  one  or  more  reporters  to  support  in  the 
General  Meeting  the  conclusions  they  have  adopted. 

ARTICLE  18 

Members  of  the  Congress  who  have  spoken  at  a  Meeting 
must,  within  twenty-four  hours,  deliver  to  the  Sectional 
Committee  a  summary  of  their  remarks,  to  enable  a  report 
of  the  proceedings  to  be  drawn  up. 

In  the  case  where  the  summary  has  not  been  submitted, 
the  wording  adopted  by  the  Secretary  or  even  the  mere 
heading  will  be  mentioned  instead. 

The  Committee  shall  have  the  right  to  request  the 


260  HIGHWAY   ENGINEERING 

author  to  abridge  his  summary,  and  should  it  not  have  been 
revised  and  amended  in  due  time,  the  Committee  will 
undertake  the  abridgement. 

ARTICLE  19 

The  summary  of  the  discussions,  arranged  and  edited 
by  the  Sectional  Committees,  together  with  the  various  con- 
clusions adopted  by  the  majority  of  the  Members  voting, 
are  transmitted  by  the  General  Reporter  to  the  Permanent 
Council  the  day  before  the  last  General  Meeting  and  they 
are  then  laid  before  the  latter  where  they  are  discussed  and 
voted  upon. 

ARTICLE  20 

A  detailed  report  of  the  Proceedings  of  each  Section  of 
the  Congress  is  prepared  by  the  Executive  Committee 
assisted  by  the  Committee  of  the  Congress  and  especially 
by  the  Vice-Presidents  and  Secretaries  mentioned  in 
Article  5. 

As  regards  the  General  Meetings  and  Excursions,  a 
similar  report  is  prepared  by  the  General  Secretary  of  the 
Session  within  the  shortest  time. 

The  joint  record  so  compiled  is  published,  under  the 
direction  of  the  Executive  Committee,  in  the  languages 
officially  recognized  by  the  Congress. 

III. — Dissolution  of  the  Association 

ARTICLE  21 

The  dissolution  of  the  Association  can  only  be  effected 
at  a  Congress  specially  convened  for  the  purpose,  and  must 
be  approved  by  a  majority  of  three-fourths  of  the  Members 
present  and  entitled  to  vote. 


APPENDIX  II  261 

ARTICLE  22 

1st.  In  the  event  of  its  dissolution,  the  liquidation  of 
the  accounts  of  the  Association  shall  be  undertaken  by  the 
Permanent  Commission. 

2d.  The  final  assets  of  the  Association  shall,  under  its 
guidance,  be  devoted  to  philanthropic  or  technical  objects 
relating  to  roads. 


AUTHOR  INDEX 


ALBERTINI,  ANTOINE  PAGB 

Address 18 

Report,  title  of 18 

Discussion 

Public  Service  Conveyances 217 

ARISI,  T. 

Address 26 

Report,  title  of 26 

Discussion 

Tires 230 

BALLO,  ALFRED 

Address 11 

Report,  title  of 11 

Discussions 

Dust  Prevention  by  the  use  of  Palliatives 95 

Garbage  Removal,  Cleaning  and  Watering 166 

BAUDRY  DE  SAUNIER,  L. 

Address 25 

Report,  title  of 25 

Discussion 

Tires 229 

BEAUMONT,  W.  WORBY 

Address 16 

Report,  title  of 16 

Discussion 

Highway  Bridges 222 

BERTHET,  E. 

Address 11 

Report,  title  of 11 

Discussion 

Garbage  Removal,  Cleaning  and  Watering 167 

BLANCH ARD,  ARTHUR  H. 

Address 5 

Report,  title  of 5 

Discussions 

Bituminous  Pavements 117 

Road  Machinery  and  Tools 159 

263 


264  AUTHOR   INDEX 

BOLTZ,    JOHANN  PAGE 

Address 7 

Report,  title  of 7 

Discussion 

Foundation  and  Drainage 76 

BONNEVIE,    AUGUSTE 

Address , 8 

Report,  title  of 8 

Discussion 

Tramways  on  Roads  and  Streets 198 

BORES  Y  ROMERO,  DON  JOSE 

Address 21 

Report,  title  of 21 

BOULNOIS,  H.  PERCY 

Address 38 

Discussion 

Economics  of  Highway  Engineering 48 

BRADACZEK,  THEODOR 

Address 4 

Reports,  titles  of 4,  24 

Discussions 

Bituminous  Surfaces 98 

Block  and  Other  Pavements 131 

Road  Signs 183 

BREDTSCHNEIDER,  AUGUST 

Address 11 

Reports,  titles  of 11,  20 

Discussions 

Economics  of  Highway  Engineering • 47 

Materials  of  Highway  Engineering 65 

Bituminous  Pavements 114 

Block  and  Other  Pavements 135 

BRET,  E. 

Address 10 

Report,  title  of 10 

Discussions 

Garbage  Removal,  Cleaning  and  Watering 162 

Removal  of  Snow  and  Ice 175 

BRODIE,  JOHN  A. . 

Address 38 

Discussion 

Economics  of  Highway  Engineering 48 


AUTHOR   INDEX  265 

CAMERMAN,  EMILE  PAQE 

Address 20 

Report,  title  of 20 

Discussion 

Materials  of  Highway  Engineering 60 

CATTANEO,  PAOLO 

Address 13 

Report,  title  of 13 

Discussions 

Economics  of  Highway  Engineering 50 

Bituminous  Pavements 116 

CHAIX,  EDMOND 

Address 24 

Report,  title  of 24 

Discussion 

Road  Signs 185 

CHRISTOPHE,  PAUL 

Address 15 

Report,  title  of '. 15 

Discussion 

Highway  Bridges 219 

CINQUE,  VICTOR 

Address 23 

Report,  title  of 23 

Discussion 

Removal  of  Snow  and  Ice 179 

COLARD,  H. 

Address 24 

Report,  title  of 24 

Discussion 

Road  Signs 184 

« 

CORAZZA,  CESARE 

Address 7 

Report,  title  of 7 

Discussion 

Bituminous  Surfaces 102 

CORNU,  Louis 

Address 20 

Report,  title  of 20 

Discussion 

Materials  of  Highway  Engineering 60 


266  AUTHOR   INDEX 

COURTOIS,  AUGUSTE  PAan 

Address 23 

Report,  title  of 23 

Discussion 

Removal  of  Snow  and  Ice 174 

CROMPTON,  COL.  R.  E. 

Address 12 

Report,  title  of , 12 

Discussions 

Economics  of  Highway  Engineering 48 

Bituminous  Pavements 115 

CROSBY,  WALTER  W. 

Address 5 

Report,  title  of 5 

Discussions 

Materials  of  Highway  Engineering 69 

Bituminous  Surfaces 103 

Bituminous  Pavements 121 

DE  FUISSEAUX,  H.  L. 

Address 17 

Report,  title  of 17 

Discussion 

Public  Service  Conveyances 210 

DE  HEEM,  PAUL 

Address 14 

Report,  title  of 14 

Discussion 

Pipe  Systems  in  Roads  and  Streets 190 

DE  HEVESY,  GUILLAUME 

Address ,. 18 

Report,  title  of 18 

Discussion 

Public  Service  Conveyances 217 

DE  JAEGERE,  ALBERIC 

Address 12 

Report,  title  of 12 

Discussions 

Macadam  and  Gravel  Roads 88 

Bituminous  Pavements 110 

Block  and  Other  Pavements 131 

DE  MORLOT,  ALBERT 

Address 141 

Discussion 

Trackways 142 


AUTHOR   INDEX  267 

DE  NOVAK,  FRANCOIS  PAGE 

Address 16 

Report,  title  of .* 16 

Discussion 

Highway  Bridges 224 

DESCANS,  LEON 

Address 15 

Report,  title  of 15 

Discussion 

Highway  Bridges 220 

DRUMMOND,  ROBERT 

Address 6 

Report,  title  of 6 

Discussions 

Bituminous  Surfaces 101 

Bituminous  Pavements 116 

ElSENLOHR 

Address 11 

Report,  title  of 11 

Discussions 

Economics  of  Highway  Engineering 47 

Bituminous  Pavements 114 

Block  and  Other  Pavements 135 

PAUL 

Address 7 

Report,  title  of 7 

Discussion 

Bituminous  Surfaces 102 

FERRUS,  COMMANDANT  L. 

Address 25 

Report,  title  of 25 

Discussion 

Tires 226 

FLECK,  GEORG 

Address 11 

Report,  title  of 11 

Discussions 

Economics  of  Highway  Engineering 47 

Bituminous  Pavements 114 

Block  and  Other  Pavements 135 


268  AUTHOR   INDEX 

FLETCHER,  AUSTIN  B.  PAGE 

Address 5 

Report,  title  of 5 

Discussions 

Economics  of  Highway  Engineering 51 

Traffic  Census 58 

Macadam  and  Gravel  Roads 92 

Bituminous  Surfaces 104 

FOCK,  EDOUARD 

Address 13 

Report,  title  of 13 

Discussion 

Block  and  Other  Pavements 137 

FORESTIER,  J.  C.  N. 

Address 38 

Discussion 

Economics  of  Highway  Engineering 41 

FOURMANOIS,  A. 

Address 13 

Reports,  titles  of 13,  24 

Discussion 

Road  Signs 184 

FRANZE,  GUSTAV 

Address 4 

Report,  title  of 4 

Discussions 

Dust  Prevention  by  the  Use  of  Palliatives 95 

Bituminous  Surfaces 100 

Bituminous  Pavements 113 

FROIDURE,  EUGENE 

Address 5 

Report,  title  of 5 

Discussions 

Economics  of  Highway  Engineering 39 

Dust  Prevention  by  the  Use  of  Palliatives 93 

Bituminous  Surfaces 98 

Block  and  Other  Pavements 133 

GALLIOT,  FRANCOIS 

Address 9 

Report,  title  of 9 

Discussion 

Tramways  on  Roads  and  Streets 199 


AUTHOR   INDEX  269 

GELINCK,  W.  G.  C.  PAGE 

Address 9 

Report,  title  of 9 

Discussion 

Tramways  on  Roads  and  Streets ,     205 

GERLACH,  FRIEDRICH 

Address . 8 

Report,  title  of 8 

Discussion 

Tramways  on  Roads  and  Streets 200 

GLASNER,  ANTOINE 

Address 6 

Report,  title  of , 6 

Discussions 

Macadam  and  Gravel  Roads 90 

Block  and  Other  Pavements 136 

GOLA,  EMILIO 

Address 20 

Report,  title  of 20 

Discussion 

Road  Machinery  and  Tools 158 

GUECHOFF,  STEFAN  CHR. 

Address 26 

Report,  title  of 26 

Discussion 

Traffic  Census 53 

GUIET,  SAMUEL 

Address 130 

Discussion 

Block  and  Other  Pavements 133 

GULLAN,  HECTOR  F. 

Address 13 

Report,  title  of 13 

HANSEZ,  JULES 

Address 17 

Reports,  titles  of 17,  25 

Discussions 

Public  Service  Conveyances 212 

Tires 225 

HEIRMANN,  EDMOND 

Address 16 

Report,  title  of 16 


270  AUTHOR   INDEX 

HENDRICKS,  C.  J.  PAGB 

Address 22 

Report,  title  of 22 

Discussion 

Footways  in  Towns  and  Cities 148 

HENNING,  JOHN 

Address 59 

Discussions 

Materials  of  Highway  Engineering 66 

Bituminous  Pavements 113 

HENTRICH,  HUBERT 

Address 14 

Report,  title  of 14 

Discussion 

Pipe  Systems  in  Roads  and  Streets 192 

HOOKER,  S.  PERCY 

Address 6 

Report,  title  of 6 

Discussions 

Economics  of  Highway  Engineering 51 

Bituminous  Surfaces 106 

HOPFNER,  PAUL 

Address 10 

Report,  title  of 10 

Discussions 

Garbage  Removal,  Cleaning  and  Watering 164 

Removal  of  Snow  and  Ice 179 

HORBURGER 

Address 11 

Report,  title  of 11 

Discussions 

Economics  of  Highway  Engineering 47 

Bituminous  Pavements 114 

Block  and  Other  Pavements 135 

HUBBARD,  PREVOST 

Address 21 

Report,  title  of 21 

Discussion 

Materials  of  Highway  Engineering 70 

ITALY,  TOURING  CLUB  OP 

Address 21 

Report,  title  of 21 

Discussion 

Materials  of  Highway  Engineering 67 


AUTHOE  INDEX  271 


JANSON,  J.  H. 

Address  ....................................................  225 

Discussion 

Tires  ...................................................  230 

JASZ,  DIDIER 

Address  ....................................................  15 

Report,  title  of  ...................................  ...........  15 

Discussion 

Pipe  Systems  in  Roads  and  Streets  .........................  196 

KARAKOULAKOFF,  PAUL 

Address  ....................................................  5 

Report,  title  of  .....................................  .........  5 

Discussions 

Macadam  and  Gravel  Roads  ..............................  89 

Dust  Prevention  by  the  Use  of  Palliatives  ..................  93 

KELLNER,  DR.  HANS 

Address  ....................................................  10 

Report,  title  of  ..............................................  10 

Discussion 

Garbage  Removal,  Cleaning  and  Watering  ..................  161 

LAFARGA,  PROSPERO 

Address  ....................................................  12 

Report,  title  of  ..............................................  12 

Discussions 

Economics  of  Highway  Engineering  ........................  50 

Block  and  Other  Pavements  .....................  .........  139 

LE  GAVRIAN,  P. 

Address  ....................................................  6 

Report,  title  of  ..............................................  6 

Discussions 

Economics  of  Highway  Engineering  ........................  42 

Macadam  and  Gravel  Roads  ..............................  90 

Dust  Prevention  by  the  Use  of  Palliatives  ..................  94 

Bituminous  Surfaces  .....................................  99 

Bituminous  Pavements  ...................................  110 

Block  and  Other  Pavements  ..............................  134 

Trackways  ..............................................  141 

LELIEVRE,  CHARLES 

Address  ....................................................  8 

Report,  title  of  ......................................  .  .......  8 

Discussion 

Foundation  and  Drainage  .................................  .78 


272  AUTHOR   INDEX 

LEMEUNIER,  RICHARD  PAOE 

Address * 11 

Reports,  titles  of 11, 14 

Discussion 

Pipe  Systems  in  Roads  and  Streets 190 

LE  Roux,  NICHOLAS 

Address 22 

Report,  title  of 22 

Discussion 

Footways  in  Towns  and  Cities 144 

LEWIS,  NELSON  P. 

Address 39 

Discussion 

Economics  of  Highway  Engineering 52 

LIDY,  GEORGES 

Address 14 

Report,  title  of - 14 

Discussion 

Pipe  Systems  in  Roads  and  Streets 190 

LLOYD  DAVIES,  D.  E. 

Address 12 

Report,  title  of 12 

Discussions 

Economics  of  Highway  Engineering 40 

Materials  of  Highway  Engineering 63 

LOPPENS,  GEORGES 

Address' 10 

Report,  title  of 10 

LUMET,  GEORGES 

Address 16 

Report,  title  of 16 

Discussion 

Tires 227 

MACHNITSCH,  RUDOLF 

Address 19 

Report,  title  of 19 

Discussion 

Road  Machinery  and  Tools 150 

MACQUET,  M. 

Address , 4 

Report,  title  of 4 


AUTHOR   INDEX  273 

MALLOCK,  A.  PAGE 

Address 16 

Report,  title  of 16 

Discussion 

Tires 229 

MARIAGE,  A. 

Address 17 

Report,  title  of .' 17 

Discussion 

Public  Service  Conveyances 212 

MAZEROLLE,  L. 

Address 12 

Report,  title  of 12 

Discussions 

Economics  of  Highway  Engineering 42 

Removal  of  Snow  and  Ice 176 

MELLO  DE  MATTOS,  JOSE 

Address 23 

Report,  title  of 23 

Discussion 

Footways  in  Towns  and  Cities 149 

MENCZER,  BELA 

Address 13 

Report,  title  of 13 

Discussion 

Block  and  Other  Pavements 137 

MESNAGER,  AUGUSTIN 

Address 21 

Report,  title  of 21 

Discussion 

Materials  of  Highway  Engineering 64 

MICHEZ,  H. 

Address 7 

Report,  title  of 7 

MIHALYFI,  JOSEPH 

Address 15 

Report,  title  of 15 

Discussion 

Pipe  Systems  in  Roads  and  Streets 196 


274  AUTHOE   INDEX 

MIKHAILOFF,  PAUL  PAGE 

Address 22 

Reports,  titles  of 22,  23 

Discussions 

Materials  of  Highway  Engineering 68 

Macadam  and  Gravel  Roads 91 

Removal  of  Snow  and  Ice 181 

MOULLE,  A. 

Address 26 

Report,  title  of 26 

Discussion 

Traffic  Census '. 54 

NAVAZZA,  AUGUSTE  . 

Address 183 

Discussion 

Road  Signs 188 

NEMETHY,  JOSEF 

Address 25 

Report,  title  of 25 

Discussion 

Road  Signs 185 

NESSENIUS,  ADOLF 

Address 141 

Discussion 

Trackways 141 

PARKER,  HAROLD 

Address 6 

Report,  title  of 6 

Discussion 

Bituminous  Pavements 124 

PELLE,  C.  F.  J. 

Address 19 

Report,  title  of 19 

Discussion 

Road  Machinery  and  Tools 151 

PENNTBACKER,  JAMES  E.  JR. 

Address 18 

Report,  title  of 18 

PlfSRISSE,  LUCIEN 

Address 17 

Report,  title  of 17 

Discussion 

Public  Service  Conveyances 214 


AUTHOR   INDEX  275 

PETERS,  FRITZ  PAGE 

Address 14 

Report,  title  of 14 

Discussion 

Pipe  Systems  in  Roads  and  Streets r~  192 

PIERCE,  VERNON  M. 

Address 7 

Report,  title  of 7 

Discussion 

Foundation  and  Drainage 83 

PIERRET,  LEOPOLD 

Address 8 

Report,  title  of 8 

Discussion 

Foundation  and  Drainage 81 

PINE,  JAMES  A.  W. 

Address 110 

Discussion 

Bituminous  Pavements 126 

PONS,  ALFRED 

Address 19 

Report,  title  of 19 

Discussion 

Road  Machinery  and  Tools 153 

Pos,  G.  A. 

Address 25 

Report,  title  of 25 

Discussion 

Road  Signs 187 

RABLIN,  JOHN  R. 

Address 12 

Report,  title  of 12 

Discussions 

Macadam  and  Gravel  Roads 92 

Dust  Prevention  by  the  Use  of  Palliatives 96 

Bituminous  Surfaces 107 

Bituminous  Pavements 127 

RESAL,  JEAN 

Address 15 

Report,  title  of 15 

Discussion 

Highway  Bridges 221 


276  AUTHOR   INDEX 

ROLDAN  Y  PEGO,  MANUEL  PAQB 

Address 23 

Report,  title  of 23 

Discussion 

Footways  in  Towns  and  Cities 149 

ROSHAUW,  J.  C. 

Address 11 

Report,  title  of 11 

Discussions 

Garbage  Removal,  Cleaning  and  Watering 169 

Removal  of  Snow  and  Ice. 180 

Ross,  CHARLES  W. 

Address 21 

Report,  title  of 21 

Discussion 

Bituminous  Surfaces 108 

SANCHIS,  VINCENT 

Address 5 

Report,  title  of 5 

Discussion 

Trackways 141 

SAUNIER,  HONORE 

Address 6 

Report,  title  of 6 

Discussion 

Bituminous  Pavements 112 

SCHLAEPFER,  ARTHUR 

Address 13 

Report,  title  of ' 13 

Discussions 

Bituminous  Surfaces 103 

Bituminous  Pavements 117 

Block  and  Other  Pavements 139 

SILCOCK,  EDWARD  JOHN 

Address 14 

Report,  title  of 14 

Discussion 

Pipe  Systems  in  Roads  and  Streets. 194 

SKOUGAARD,  J. 

Address 4 


AUTHOR  INDEX  277 


SKOUGAARD,  J. 

Report,  title  of  ...........  •  ...................................         4 

Discussions 

Foundation  and  Drainage  .................................      82 

Macadam  and  Gravel  Roads  ..............................       91 

Dust  Prevention  by  the  Use  of  Palliatives  ..................       96 

SMITH,  EDWARD  SHRAPNELL 

Address  ....................................................       17 

Report,  title  of  ...........................  .  ..................       17 

Discussion 

Public  Service  Conveyances  ...............................     215 

SMITH,  J.  WALKER 

Address  ....................................................       39 

Discussion 

Economics  of  Highway  Engineering  ........................       49 

SPANGLER,  LUDWIG 

Address  .  :  ..................................................  23 

Report,  title  of  ...........................  ...................  23 

Discussion 

Removal  of  Snow  and  Ice  .................................  171 

SPERBER, 

Address  ....................................................  4 

Report,  title  of  ..............................................  4 

Discussions 

Dust  Prevention  by  the  Use  of  Palliatives  ..................  95 

Bituminous  Surfaces  .....................................  100 

Bituminous  Pavements  ......  .............................  113 

SPITERI,  JOSE  RODRIGUEZ 

Address  ...........................................  .  ........  9 

Reports,  titles  of  ............................................  9,  10 

Discussions 

Garbage  Removal,  Cleaning  and  Watering  ..................  169 

Tramways  on  Roads  and  Streets  .........................  .  .  207 

STEFFELAAR,  L.  C. 

Address  ....................................................       16 

Report,  title  of  ..............................................       16 

Discussion 

Tires  ...................................................     230 

STEUERNAGEL,  KARL 

Address  ....................................................       14 

Report,  title  of  ..............................................       14 

Discussion 

Pipe  Systems  in  Roads  and  Streets  .........................     192 


278  AUTHOR  INDEX 

TEDESCHI,  MASSIMO  PAGE 

Address 7 

Report,  title  of 7 

Discussion 

Bituminous  Surfaces 102 

THOMAS,  EDMOND 

Address 19 

Report,  title  of 19 

Discussion 

Road  Machinery  and  Tools 151 

TOLLER,  GINO 

Address 9 

Reports,  titles  of 9,  25 

Discussions 

Road  Signs 187 

Tramways  on  Roads  and  Streets 204 

TRUSLER,  GEORGE  D. 

Address 22 

Report,  title  of 22 

Discussion 

Footways  in  Towns  and  Cities 147 

TSVETKOVSKY,  CONSTANTIN 

Address 22 

Report,  title  of 22 

Discussion 

Materials  of  Highway  Engineering 68 

TUR,  PAUL 

Address 189 

Discussion 

Pipe  Systems  in  Roads  and  Streets 192 

ULLMAN,  G. 

Address 8 

Report,  title  of 8 

Discussion 

Tramways  on  Roads  and  Streets 198 

VANDONE,  ITALO 

Address 8 

Reports,  titles  of 8,  26 

Discussions 

Traffic  Census 57 

Foundation  and  Drainage .82 


AUTHOR   INDEX  279 

VAN  HEYST,  D.  A.  PAGE 

Address 9 

Report,  title  of 9 

Discussion 

Tramways  on  Roads  and  Streets 205 

VAN  LOBEN  SELS,  M.  J. 

Address 22 

Report,  title  of 22 

Discussions 

Materials  of  Highway  Engineering 68 

Block  and  Other  Pavements 138 

VAN  MEERBEECK,  H. 

Address 24 

Report,  title  of 24 

Discussion 

Road  Signs 184 

VAN  VOLSOM,  EDGARD 

Address 7 

Report,  title  of 7 

Discussion 

Foundation  and  Drainage 76 

VAN  ZEEBROECK,  ED. 

Address ' 24 

Report,  title  of 24 

Discussion 

Road  Signs 184 

VERGER,  CASIMIR 

Address 20 

Report,  title  of 20 

Discussion 

Road  Machinery  and  Tools 155 

VERSTRAETE,  RICHARD 

Address '. , 5 

Report,  title  of 5 

Discussions 

Economics  of  Highway  Engineering 39 

Dust  Prevention  by  the  Use  of  Palliatives 93 

Bituminous  Surfaces 98 

Block  and  Other  Pavements 133 

VON  MONTIGNY, 

Address 14 

Report,  title  of 14 

Discussion 

Pipe  Systems  in  Roads  and  Streets 192 


280  AUTHOR   INDEX 

VON  SCHOLTZ,  A.  PAGB 

Address  ....................................  .................  14 

Report,  title  of  ..............................................  14 

Discussion 

Pipe  Systems  in  Roads  and  Streets  .........................  192 


VON  SzTRtfKAV,  STEFAN 

Address^  ...................................................         9 

Reportf  title  of  ..............................................         9 

Discussion 

Tramways  on  Roads  and  Streets  ...........................     203 

WAICHT,  CESLAV 

Address  ....................................................       20 

Report,  title  of  ..............................................       20 

Discussion 

Road  Machinery  and  Tools  .........................  ......     158 

WAKELAM,  H.  T. 

Address  ....................................................       18 

Reports,  titles  of  ...........................  .................  18,  19 

Discussion 

Road  Machinery  and  Tools  ...............................     157 

WALBAUM,  LUDWIG 

Address  ....................................................       20 

Report,  title  of  ...............................................       20 

Discussion 

Materials  of  Highway  Engineering  .........................       60 

WALLAND,  C.  B.  S. 

Address  .............................  .......................       15 

Report,  title  of  ..............................................       15 

Discussion 

Tramways  on  Roads  and  Streets  ...........................     206 

WABREN,  GEORGE  C. 

Address  ....................................................     110 

Discussion 

Bituminous  Pavements  ...................................     127 

WENNER,  VICTOR 

Address  ....................................................  13 

Report,  title  of  ..............................................  13 

Discussions 

Bituminous  Surfaces  .....................................  103 

Bituminous  Pavements  ...................................  117 

Block  and  Other  Pavements.  .                                            .....  139 


AUTHOR  INDEX  281 

WILHELM,  IVAN  PAGE 

Address 23 

Report,  title  of... 23 

Discussion 

Removal  of  Snow  and  Ice 178 

WILLIAMS,  BENJAMIN  W. 

Address 210 

Discussion 

Public  Service  Conveyances 216 

WYNNE-ROBEKTS,  R.  O. 

Address 9 

Reports,  titles  of 9,  21 

Discussions 

Bituminous  Surfaces 101 

Tramways  on  Roads  and  Streets 202 

YABBICOM,  THOMAS  H. 

Address. 10 

Report,  title  of 10 

Discussions 

Garbage  Removal,  Cleaning  and  Watering 165 

Removal  of  Snow  and  Ice 179 


SUBJECT  INDEX 

ABRASION  test,  64 

Aeberli  method,  114 

Aitken  distributor,  use  for  surface  treatment,  107 

Asphalt 

analysis  for  detection  of  coal  tar  in,  63 

desirability  as  a  flush  coat,  127 

methods  of  analysis  for  rock  asphalt,  64,  65 

mixed  with  asphaltic  oil,  124,  126 

requisite  qualities  of  rock  asphalt,  62 

temperature  to  which  it  is  heated,  124 

See  Asphalt  pavements,  Bituminous  materials,  Bituminous  pavements, 

Bituminous  surfaces 
Asphalt  block  pavements 

conclusions  relative  to,  239 

construction  of  115,  117 

trial  of,  47 

use  on  bridge  floors,  40 
Asphaltic  oils 

analysis  of,  See  table,  70 

temperature  to  which  oil  is  heated,  124 

use  of,  67,  122,  123,  124 

See  Bituminous  materials,  Bituminous  surfaces 
Asphalt  pavements 

conclusions  relative  to,  238 

construction  of,  40,  115,  116,  126 

cost  of,  43,  47,  110 

dust  on,  44 

effect  of  urine  on,  40 

maximum  grade  of,  45 

noise  of,  43 

sanitariness,  45 

Blipperiness,  44,  47 

use  of,  40,  50,  110,  117,  165 
next  to  rails,  45,  201,  206 
on  bridges,  40 
Austria 

Bituminous  surfaces,  98 

Block  and  other  pavements,  131 

283 


284  SUBJECT   INDEX 

Austria 

Garbage  removal,  cleaning  and  watering,  161 

Foundation  and  drainage,  76 

Materials  of  highway  engineering,  60 

Removal  of  snow  and  ice,  171 

Road  machinery,  150 

Road  signs,  183 

Tramways,  198 
Automobiles,  See  Motorbuses,  Motor  vehicles,  Tires,  Wheels 

BEDEAU  System,  112 
Belgium 

Bituminous  pavements,  110 
Bituminous  surfaces,  98 
Block  and  other  pavements,  131,  133 
Dust  prevention  by  use  of  palliatives,  93 
Economics  of  highway  engineering,  39 
Foundation  and  drainage,  76 
Highway  bridges,  219,  220 
Macadam  and  gravel  roads,  88 
Materials  of  highway  engineering,  60 
Pipe  systems,  190 

Public  service  conveyances,  210,  212 
Removal  of  snow  and  ice,  174 
Road  machinery,  151 
Road  signs,  184 
Tires,  225 
Tramways,  198 
Binders 

cement  as  a  binder,  134 
conclusions  relative  to,  232,  238 
effect  of  climate  on  choice  of  binding  material,  39 
limestone,  89 
Tina,  63 

See  Asphaltic  oils,  Bituminous  pavements,  Bituminous  surfaces 
Bituminous  materials 

requisite  qualities  of,  62,  69 
table  of  analyses,  70 
value  of  tests  for 

distillation,  75 

fixed  carbon,  74 

flash  point,  72 

free  carbon,  73 

insolubility  in  88°  B.  naphtha,  74 

melting  point,  72 


SUBJECT    INDEX  285 

Bituminous  materials,  value  of  tests  for 

penetration,  72 

solubility  in  carbon  bi-sulphide,  73 

specific  gravity,  72 

volatilization,  73 

See  Asphalt,  Asphaltic  oils,  Asphalt  pavements,  Bituminous  pave- 
ments, Bituminous  surfaces,  Tar 
Bituminous  pavements 
Aeberli  method,  114 
amount  of  traffic  on,  48 
construction, 

essentials  of,  129 

mixing  method,  113,  llS,  llG^  118,  120,  121,  125,  127 

penetration  method,  111,  1^4, ;i  18",  121,  122t  123,  124,  126,  127 
cost  of,  49,  112,  115,  116,  119>  120 ,  £ • , 
crown,  115 

flush  coat,  120,  127  '.':£•  :  • ; 

hand  mixing-  127  . 

heating  bituminous  materials,  121,  124,  127 
life  of,  48,  118,  119 
mixing  machines,  113,  128,  159 
pitch  macadam,  111 
rolling,  116,  121,  124,  125 
substitution  for  stone  block,  49 
tar  macadam,  50,  110,  114,  117 
tar,  soap,  and  clay  as  a  binder,  111,  113 
tarvia,  111 

See  Bituminous  materials,  Asphalt  pavements 
Bituminous  surfaces 

amount  of  bituminous  material  used,  103,  104,  107 
amount  of  screenings  used,  106 
burning  tar,  99 

comparison  of  hand  and  machine  methods,  99,  100,  102 
conclusions  relative  to  superficial  tarring,  233,  234 
.   cost  of,  46,  49,  101,  102,  103,  105,  106 
crown,  105 

effect  of  wet  weather  and  shady  location  on,  101 
effect  on  trees,  41 

life  of,  42,  99,  101,  102,  105,  106,  108 
machine  distribution,  98,  99,  100,  107 
method  of  constructing  gravel  surfaces  with  oil,  107 
oil  mixed  with  sand,  108 
penetration,  depth  of,  104 

preparation  of  surface  to  be  treated,  99,  100,  102,  103,  104,  106 
rolling,  101 


286  SUBJECT    INDEX 

Bituminous  surfaces 

temperature  to  which  material  is  heated,  99 

thinning  tar,  99,  100,  104 

traffic  on,  48 

use  of  refined  and  crude  tars,  102 

use  of  sand  and  stone  dust,  100,  101,  102,  103,  104,  106,  107 

See  Bituminous  materials,  Tar 
Brick 

analyses  of  clay,  69 

broken  brick  as  a  foundation,  77,  78 

size  of,  68,  138,  140 

See  Brick  pavements 
Brick  pavements 

advantages  of,  139 

construction  of,  133,  138 

joint  filler,  138 

use  of,  68 

use  of  next  to  rails,  206 
Bridges 

design  of  stringers,  220 

influence  of  motor  vehicles  on,  220,  221,  222,  223,  224,  240 

specified  loading  on,  219,  224 

testing  of  by  representative  loads,  240 

use  of  asphalt  in  bridge  floors,  40 
Broken  stone 

as  a  foundation  for  pavements,  77 

See  also  Drainage,  Macadam 
Brooms 

description  of,  153 

use  of,  162 

See  Sweeping 
Bulgaria 

Dust  prevention  by  the  use  of  palliatives,  93 

Macadam  and  gravel  roads,  89 

Traffic  census,  53 

CALCIUM  chloride,  use  as  a  palliative,  93,  94,  95,  96 

See  Dust  palliatives 
Carriageways 

location  of  pipes  in,  See  kind  of  pipes  in  question 

width  of,  144,  147,  208 
Cement,  See  Concrete 
Cleaning,  See  Sweeping,  Sprinkling 

Coal  tar,  See  Bituminous  materials,  Bituminous  surfaces,  Bituminous  pave- 
ments, Tar 


SUBJECT   INDEX  287 

Conclusions,  See  subject  in  question 
Concrete 

concrete  pavement,  133,  136 

cost  of,  134 

proportions  of,  78 

reinforced  concrete  pavement,  134 

slag  concrete,  77 

thickness  of,  82,  85 

See  Foundations 
Conduits 

depth  of,  190 

location  of,  190,  191,  193,  194,  196 
Congress 

attendance,  1,  3 

committees,  248,  249,  250,  251 

discussions,  246,  259,  260 

dissolution  of,  260 

fees  and  dues,  248,  249,  250,  252,  254,  255 

laboratory,  244,  245,  251 

library,  244,  252 

Local  Organizing  Commission,  249,  253 

membership,  28,  244,  248,  250,  254,  255,  256 

object  of,  247 

Permanent  Council,  2,  248,  250,  252 

Permanent  International  Commission,  1,  244, 245, 247, 248,  249,  250,  252, 
256 

reports,  246,  249,  252,  255,  256,  257,  258,  259 
Cost,  See  articles  in  question 


construction  between  rails  at,  198,  205 

See  Road  signs,  Tramways 
Crown 

of  bituminous  pavements,  115 

of  bituminous  surfaces,  105 
Culverts, 

construction  of,  82 

See  Drainage 
Curbs,  necessity  for,  146 

DANGER  signals,  See  Road  signs 
Determination, 

amount  of  clay,  65 

carbonate  of  lime,  65 

coal  tar  in  asphaltic  compounds,  63 

dripping  point,  66 


288  SUBJECT    INDEX 

Determination, 

melting  point,  66 

percentage  of  sulphur,  66 

resistance  to  wear  of  stones,  64 

solubility  in  chloroform,  65 

specific  gravity,  66 

See  table  of  analyses,  70 
Distillation,  value  of  test,  75 
Distributor, 

Aitken,  use  of,  107 

comparison  of  hand  and  machine  methods,  99,  100,  102 
Ditches,  See  Drainage 
Drainage, 

by  ditches,  80,  82,  86 

by  excavating  and  adding  new  material,  91 

by  percolation  pits,  80 

conclusions  as  to,  235 

construction  of  V-drain,  87 

depth  and  grade  of  underground  drains,  81 

of  car  track,  202,  209 

of  earth  foundations,  84 

surface  drainage,  86 

tile  pipe,  86 

Dust  carts,  description  of,  167 
Dust  palliatives 

calcium  chloride,  93,  94,  95,  96 

conclusions  relative  to,  234 

emulsions,  95 

magnesium  chloride,  94,  95 

petroleum  oil,  95 

sea  water,  170 

sodium  chloride,  94,  95 

EGYPT 

Economics  of  highway  engineering,  40 

Materials  of  highway  engineering,  63 
Emulsions 

use  of  palliatives,  95 

See  Dust  palliatives 
Evaporation,  value  of  test,  73 
Excursions 

to  Avenue  Tervueren,  35 

"  Citadel  of  Namur,  36 

"  Gilleppe  Dam,  36 

"  Grottoes  of  Han,  36 


SUBJECT    INDEX  289 


Excursions, 

to  Lessines,  35 

"  Montfort,  35 

"  Quenast,  34  • 

"  Waterfalls  of  Coo,  36 
Exhibitions 

cycling  track,  31 

kleinpflaster,  32 

machinery,  33 

macadam,  30 

Roman  pavement,  29 

sheet  asphalt,  30 

stone  block  pavement,  30,  31 

tar  macadam,  30,  32 

Tresaguet  method,  30,  32 

vitrified  brick,  30,  31 

FIXED  carbon,  value  of  test,  74 
Flash  point,  value  of  test,  72 
Flushing 

description  of  flushing  machine,  165 

removal  of  snow  by,  176,  179 
Footways 

construction  with  asphalt,  145,  147 
"     brick,  148 
"     cement,  145 
"     granite  slabs,  146 
"     stone  blocks,  146,  149 

curbs,  146 

location  of  pipes  in,  See  services  in  question 

removing  snow  from,  179 

sweeping  of,  163,  166,  167 

transverse  slope  of,  144,  145,  147,  148 

width  of,  144,  147,  148,  196 
Foundations 

broken  stone,  77 

comparative  resistance  of  different  materials  as,  79 

conclusions  relative  to,  234 

concrete  foundations,  78,  82,  84,  85,  201 

concrete  slab  block,  77,  194 

different  methods  used,  79,  85 

use  of  telford,  76,  84 
France 

Bituminous  pavements,  110,  112 

Bituminous  surfaces,  99 


290  SUBJECT   INDEX 

France 

Block  and  other  pavements,  133,  134 

Dust  prevention  by  the  use  of  palliatives,  94 

Economics  of  highway  engineering,  41,  42 

Footways,  144 

Foundation  and  drainage,  78,  81 

Garbage  removal,  cleaning  and  watering,  162 

Highway  bridges,  221 

Macadam  and  gravel  roads,  90 

Materials  of  highway  engineering,  64 

Pipe  systems,  190,  192 

Public  service  conveyances,  213,  214 

Removal  of  snow  and  ice,  175,  176,  178 

Road  machinery,  151,  153,  155 

Road  signs,  185 

Tires,  226,  227,  229 

Trackways,  141 

'Traffic  census,  54 
Free  carbon,  value  of  test,  73 

GALGATINE,  definition  of,  113 
Garbage,  removal  of,  162 
Gas  pipes 

danger  of  in  subways,  192 

depth  of,  190,  196 

location  of,  190,  191,  193,  196 
Gauge,  See  Tramways 
Germany 

Bituminous  pavements,  113,  114 

Bituminous  surfaces,  100 

Block  and  other  pavements,  135 

Dust  prevention  by  the  use  of  palliatives,  95 

Economics  of  highway  engineering,  47 

Garbage  removal,  cleaning  and  watering,  164 

Materials  of  highway  engineering,  65,  66 

Pipe  systems,  192 

Removal  of  snow  and  ice,  179 

Tramways,  200 

Trackways,  141 
Grade 

of  asphalt  pavements,  45 

of  wood  block  pavements,  44 

Granite  block  pavements,  See  Stone  block  pavements 
Gravel  roads 

constructed  with  bituminous  materials,  125 


SUBJECT    INDEX  291 


Gravel  roads 

use  of  in  Holland,  68 
Great  Britain 

Bituminous  pavements,  115,  116 

Economics  of  highway  engineering,  48,  49 

Footways,  147 

Garbage  removing,  cleaning  and  watering,  165 

Highway  bridges,  222 

Pipe  systems,  194 

Public  service  conveyances,  215,  216 

Removal  of  snow  and  ice,  179 

Road  machinery,  157 

Tires,  229 

Tramways,  202 

HAND  mixing,  See  Bituminous  pavements 
Harrow,  for  smoothing  snow,  181 
Hedge,  as  a  snow  fence,  182 
Hungary 

Block  and  other  pavements,  136,  137 

Dust  prevention  by  the  use  of  palliatives,  95 

Garbage  removal,  cleaning  and  watering,  166 

Highway  bridges,  224 

Macadam  and  gravel  roads,  90 

Pipe  systems,  196 

Public  service  conveyances,  217 

Road  signs,  185 

Tramways,  203 

Hydrants,  use  of  in  street  flushing,  167 
Hygiene 

germ  content  in  soils,  169 

of  asphalt  pavements,  47 

of  wood  block  pavements,  46 

ITALY 

Bituminous  pavements,  116 
Economics  of  highway  engineering,  50 
Foundation  and  drainage,  82 
Materials  of  highway  engineering,  67 
Public  service  conveyances,  217 
Removal  of  snow  and  ice,  179 
Road  machinery,  158 
Road  signs,  187 
Tires,  230 
Traffic  census,  57 
Tramways,  204 


292  SUBJECT    INDEX 

JOINT  fillers 

See  Brick  pavements 

See  Stone  block  pavements 

KLEINPFL ASTER,  See  Stone  block  pavements 

LEGISLATION 

regulating  wjdth  of  tires,  etc.,  228,  231 

regulating  maintenance    of    roads    occupied    by  railways,    199,  204, 

237 

Lighting  cables,  See  Conduits 
Lime,  See  Binders 
Loads,  See  Bridges,  Wheels,  Tires 
Location 

pipe  services,  See  Conduits,  Gas  pipes,  Water  pipes 

sewers,  See  Sewers 

tracks,  See  Tramways 

MACADAM 

conclusions  relative  to,  237 

cost  of,  43,  46,  51,  89 

dust  from,  44 

effect  of  climate  on  choice  of  binding  materials,  39 

foundation,  76,  79,  81,  88 

materials,  60,  63,  90,  92 

methods  of  construction,  88,  90,  91,  92 

noise  of,  43 

raised  shoulder,  80 

repair  of,  44,  51 

rolling  of,  89 

tests  of  materials,  61,  64 

treatment  of  in  wet  weather,  169 

use  of,  47,  50,  165 

use  of  next  to  and  between  rails,  45 
Magnesium  Chloride,  use  as  a  palliative,  94,  95 
Maintenance,  See  subject  in  question 
Melting  point 

determination  of,  66 

value  of  test,  72 

Method  of  analysis,  See  determination  of 
Mixing  machinery,  113,  128,  159 

See  Bituminous  pavements 
Mixing  method,  See  Bituminous  pavements 
Monaco 

Garbage  removal,  cleaning  and  watering,  167 


SUBJECT   INDEX  293 

Motorbuses 

advantages  of,  210,  214,  215,  217,  218 

capacity  of,  212,  217 

conclusions  relative  to,  241,  243 

cost  of  operation,  212 

cost  of  road  maintenance  necessitated  by  the  use  of,  213,  216 

disadvantages  of,  211,  215 

Renard  system,  213,  217 

tires,  213 

traffic  on,  216 

weight  of,  212 

See  Motor  vehicles,  Tires 
Motor  vehicles 

action  on  road,  225,  241 

braking  car  on  road,  229 

limits  as  regards  speed  and  weight,  228 

skidding,  225 

See  Motorbuses,  Sprinklers,  Sweepers,  Tires 
Mud,  collection  of  by  scraper,  168 

NAPHTHA  insoluble,  value  of  test,  74 
Netherlands 

Block  and  other  pavements,  138 

Footways,  148 

Materials  of  highway  engineering,  68 

Road  signs,  187 

Tires,  230 

Tramways,  205,  206 
Noise,  See  pavement  in  question 
Non-skid  devices,  See  Tires 
Norway 

Dust  prevention  by  the  use  of  palliatives,  96 

Foundation  and  drainage,  82 

Garbage  removal,  cleaning  and  watering,  169 

Macadam  and  gravel  roads,  91 

Removal  of  snow  and  ice,  180 

OILED  roads 

comparative  results  obtained  using  oil  and  tar,  107 

use  of,  95,  105,  107,  108 

See  Asphaltic  oils,  Bituminous  surfaces 

PAVEMENTS 

See  Asphalt,  Bituminous,  Brick,  Concrete,  Stone  block,  Wood  block  pave- 
ments 


294  SUBJECT    INDEX 

Pipe  systems 

See  Conduits,  Gas  pipes,  Sewers,  Water  pipes 
Pitch  Macadam,  See  Bituminous  pavements 
Penetration,  value  of  test,  72 
Penetration  method,  See  Bituminous  pavements 
Petroleum,  See  Asphaltic  oils 
Portugal 

Footways,  149 

RAILS,  See  Tramways 
Railways,  See  Tramways 
Reinforced  concrete 

Reinhardt  blocks  for  rail  foundation,  201 
Reinforced  macadam,  134 
Road  administration 

commission  to  govern  public  service  installations,  190,  191,  192,  194,  239 

maintenance  of  road  occupied  by  the  railways,  199,  204,  237 
Road  Congress,  See  Congress 
Road  machinery 

See  Distributors,  Flushing,  Mixing  machinery,  Rollers,  Scarifiers,  Snow 

Sprinklers,  Sweepers 
Road  signs 

danger  signals,  184,  185,  186,  187 

distance  from  obstacle,  185,  188 

marking  of,  184,  186 

size  of  signals,  184,  185 
Rock  asphalt 

See  Asphalt,  Asphalt  pavements 
Rollers 

advantages  of  oil  driven  roller,  151,  152,  153 

cost  of  operating  rollers,  157 

hand  roller,  150 

Laffly  roller,  152 

petrol  driven  rollers,  151,  157 

Salmson  &  Contant  roller,  152 

steam  rollers,  159 
Rolling 

bituminous  pavements,  116,  121,  124,  125 

block  pavements,  46 

macadam  roads,  89 

theory  of,  151 
Russia 

Macadam  and  gravel  roads,  91 

Materials  of  highway  engineering,  68    ' 

Removal  of  snow  and  ice,  181 


SUBJECT    INDEX  295 


Russia 

Road  machinery,  158 

SAND 

as  a  foundation,  77,  78 

for  overcoming  slipperiness,  168 

heating  of,  125 

use  on  superficial  coats,  100,  101,  102,  106,  107 
Scarifiers 

amount  of  work  done,  154 

Bobe  scarifier,  154,  155 

cost  of  scarifying,  154,  156 

Econome  scarifier,  159 

Morrison  scarifier,  154,  155 

repairs  on,  155 

Zettelmeyer  scarifier,  155 
Scarifying 

amount  of  work  done,'  154 

cost  of,  154,  156 

Sea  water,  use  of  for  sprinkling,  170 
Sewers 

carrying  away  sweepings  in,  164 

carrying  away  snow  in,  175,  176,  179 

location  of  in  street,  191,  195,  196 

location  of  in  suburban  roads,  193 
Shade,  effect  on  surface  tarring,  101 
Shoulders,  80 
Sidewalks,  See  Footways 
Sign  posts,  See  Road  signs 
Slag 

analysis  of,  67 

as  a  foundation  for  pavements,  77,  85 
Slipperiness 

asphalt  pavements,  44 

remedying  of,  168 

stone  block  pavements,  44 

wood  block  pavements,  44 
Snow 

cleaning  grooves  in  rails,  173 

cost  of  removal,  180 

depth  of  snow,  174 

melting  snow,  178,  180 

methods  used  in  high  altitudes,  178 

preparation  of  road  for  sleighing,  180,  181 

removal  by  flushing  through  special  conduits,  179 


296  SUBJECT    INDEX 

Snow 

removal  by  salt,  175,  176,  179 

rotary  brushes  for  cleaning,  173,  176,  177 

salting  machine,  177 

snow  fences,  174,  182 

snow  plows,  172,  173,  174,  175,  178,  179,  181 

specifications  for  salt,  177 

time  at  which  to  commence  work,  173,  174,  178 
Sodium  chloride,  use  as  a  palliative,  94,  95 
Soils 

conclusions  as  to  soils  for  foundation  and  drainage,  235 

germ  content  in  soils,  169 
Spain 

Block  and  other  pavements,  139 

Economics  of  highway  engineering,  50 

Garbage  removal,  cleaning  and  watering,  169 

Trackways,  141 

Tramways,  207 
Specific  Gravity 

determination  of,  66 

value  of  test,  72 

Specifications,  bridge  loads,  219,  224 
Sprinklers 

combined  sweepers  and  sprinklers,  169 

motor  driven  sprinklers,  94,  154,  156,  162,  165,  237 

sprinkler  supplied  with  pressure,  170 
Sprinkling 

amount  of  water  used,  163,  164 

conclusions  relative  to,  237 

cost  of,  168 

methods  used,  166,  167,  168 

necessity  for,  161 
Stone  block  pavements 

amount  of  traffic  on,  48 

cobblestone,  131,  139 

conclusions,  relative  to,  238 

construction  of,  132,  136,  137,  139,  140 

cost  of,  43,  46,  139 

dust  from,  44 

ease  of  repair,  44 

foundation  for,  77,  81 

joint  fillers,  135,  136,  137 

kleinpflaster,  32,  131,  136 

materials  used,  132,  135 

noise  of,  43 


SUBJECT    INDEX  297 

Stone  block  pavements 

sanitariness,  45 

slipperiness,  44 

tests  for  stone  blocks,  64 

use  of,  45,  49,  50,  165,  206 
Subdrains,  See  drainage 
Subways 

cost  of,  190,  195 

See  Conduits,  Gas  pipes,  Sewers,  Water  pipes 
Superficial  tarring,  See  Bituminous  surfaces 
Sweepers 

combined  sweepers  and  sprinklers,  169 

cost  of  repairs,  157 

motor  sweepers,  156 

pick  up  sweepers,  153,  158,  165 

sweeping  plants,  162 
Sweeping 

conclusions  relative  to,  237 

disposal  of  sweepings,  165,  166,  168,  169 

methods  used,  166,  167,  169 
Switzerland 

Bituminous  pavements,  117 

Bituminous  surfaces,  102,  103 

Block  and  other  pavements,  139 

Road  signs,  188 

Trackways,  142 

TAR 

analyses  of,  70 

cost  of,  98 

effect  on  plants  and  trees,  41 

life  of,  42 

use  of,  67,  111,  118,  119,  123,  124 

detection  of  in  asphaltic  compounds,  63 

See  Bituminous  materials,  Bituminous  pavements,  Bituminous  surfaces 
Telford,  See  Foundation 
Telephone  cables,  See  Conduits 
Temperatures 

heating  asphaltic  oils,  124 

heating  bituminous  materials,  121,  124,  127 

heating  sand,  125 
Tile,  See  Drainage 
Tina,  analysis  of,  64 
Tires 

action  of  pneumatic  tires  on  road  surfaces,  225,  229,  230 


298  SUBJECT    INDEX 

Tires 

air  pressure  and  tractive  force,  226 

effect  of  narrow  tires,  241 

greatest  pressure  on,  228 

non-skid  devices,  226,  227,  243 

saving  of  fuel,  230 

solid  tires,  227,  229 

twin  tires,  226,  230 
Tools 

See  Brooms,  Distributors,  Mixing  machinery,  Rollers,  Scarifiers,  Snow, 

Sprinklers,  Sweepers 
Total  bitumen 

solubility  in  carbon  bisulphide,  73 
Trackways 

conclusions  relative  to,  233 

construction  of,  142 

use  of,  141,  142 

wear  of,  142 

Traction,  resistance  of,  46 
Traffic  census 

amount  of  traffic  necessitating  different  types  of  construction,  48 

coefficients  of  reduction,  55 

importance  of,  56 

methods  used,  53,  54,  55,  56 

of  roads  in  Massachusetts,  U.  S.  A.,  58 

tonnage,  55 
Tramways 

accidents,  199 

clear  width  of  carriageway,  208 

conclusions  relative  to,  235 

construction  of  track  on  bridges,  205 

construction  of  road  surface  next  to  rails,  202,  208 

drainage  of  track,  202,  209 

foundation  for  track,  199,  201,  206,  208 

gauge  of  track,  198,  205 

increased  cost  of  road  maintenance,  199,  200,  204,  237 

location  of  track,  198,  200,  203,  204,  205,  207,  236 

paving  at  crossings,  198,  205 

rails,  198,  203,  204,  205,  206 

rail  joints,  204,  208 
Trees 

conclusions  relative  to,  236 

harmful  effect  of  tar  on,  41 

placing  on  footways,  146,  147 

planting  of  trees,  240 


SUBJECT    INDEX  299 

UNITED  STATES 

Bituminous  pavements,  117,  121,  124,  126,  127 
Bituminous  surfaces,  103,  104,  106,  107,  108 
Dust  prevention  by  the  use  of  palliatives,  96 
Economics  of  highway  engineering,  51,  52 
Foundation  and  drainage,  83 
Macadam  and  gravel  roads,  92 
Materials  of  highway  engineering,  69,  70 
Road  machinery,  159 
Traffic  census,  58 

WALKS,  See  Footways 
Water  gas  tar 

analysis  of,  See  table,  70 

See  Bituminous  materials,  Tar 
Watering,  See  Sprinkling 
Water  pipes 

depth  of,  190,  196 

location  of,  190,  191,  193,  196 

use  of  double  mains,  192,  239 
Westrumite,  Use  of,  94 
Wheel 

diameter  of,  228 

relation  of  width  of  tire  and  diameter  of  wheel,  227,  231,  241,  242 

spring  wheels,  227,  230 
Width 

See  Carriageways,  Footways 
Wood  block  pavements 

conclusions  relative  to,  238 

construction  of,  132,  136 

cost  of,  43,  47 

dust  from,  44 

grade  of,  44 

harmfulness  of  constant  watering,  161 

noise  of,  43 

repair  of,  44 

eanitariness,  46  / 

slipperiness,  44 

tests  of  wood  blocks,  62,  138 

use  of,  45,  50,  137,  140,  165,  201 


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